How to convince parents for inter religious marriage

Marriage between the boy and girl belonging to different communities or societies has become a common thing in the modern times and there is no big deal in that. But the point is about the compatibility between the couple.
Marriage is a lifetime relationship and is not a matter of joke or casual talks. The decision for marriage is to be taken after a lot of deliberation and thinking.
In young age many people fall in love but it is difficult to find out that it is the real love or infatuation of the young minds. If it is infatuation then it is better to close that chapter and divert attention to other positive and constructive arenas.
True love can be identified by certain feelings generated by it. Some of these are faith and mutual sacrifice for each other, devotion and dedication to the common objectives of the family, caring and concern for each other, manage the household within the financial position one has etc. If one is sure of those things then it makes sense to go ahead in the relationship.
There are certain things which might create problems in the longer run and some of them are having difference in financial conditions, difference of religion, difference in the interest areas of the couple, social inhibitions etc.
Before the marriage many parents do not object for it but after the marriage they start to create problems due to various reasons and then boy is forced to live separately.
How you are sure that girl's parent will not create any problem for you later. Same thing is applied to your parents also. When the girl is ready to live with you in your house then what is the guarantee that your parents will accept her whatever way she wants to live in your house. You must understand that even in an arranged marriage problems can crop up with time. In case of inter community or inter caste or inter religion marriages the complications are expected and can create problems. Parents generally bother for the society in which they live rather than the love relationship of the their children.
Let us understand some other possibilities in this case. Suppose her parents debar her from their property and your parents also show no interest in supporting you then what are the financial resources with you to survive in this tough and cruel world? If you have some ideas in this respect then permission of parents would not be required for this relationship and you can go ahead with this marriage with mutual consent even registering it in the marriage registrar office without taking cognisance of each other's religion. Sometimes religion itself becomes a big hindrance in such cases.
There are three possibilities in this case - the girl changes her religion in your favour, you change it in her favour, or both of you leave your religion and live as cosmopolitan citizens without adhering to any religion.
If religion is not an issue then it would be easy to go ahead with this relationship.
So you have to consider all these aspects and resolve and find the solutions before going ahead otherwise you would invite problems in the future.
Today you are ready to do everything that the girl wants but tomorrow if you are not able to show same dedication then the relationship might turn sour and then girl will also go on backfoot which would be a shock for you.
I would suggest you to consider all these points and then take a proper decision.

It is a grand idea to have the permanent relationship with a Muslim Girl and there is no objection from three civilised families if there is the culmination of such an inter cast marriage but whatever we call that relationship- infatuation or emotional attachment, this bondage might weaken due to course of time and though it looks simple at the first glance, it is not that much easy if we consider several variables to be thought of seriously before the culmination such alliance. The following points must be considered before you tie a knot with that Muslim Girl.
1) Closely watch the culture of the family of your would be spouse. You have to see how your mother and father in laws are treating you and see how much comfortable they are with you in sharing their family issues and the same case applies with the other in laws.
2) Talk in length with your would be spouse stretching from financial issues to management of household and her emotional bondage with you. Ensure that she can be relied upon in the hours of crisis. Such an analysis would make you comfortable in clinching this deal.
3) Consider the financial angle prior to finalisation of this marriage so that you don't have to suffer later once you are blessed with kids for which enough resources would be required in the different situations such as their bringing ups with the choice of right schools and proper medical maintenance and other expenses. Hence you should be good planner with sufficient funds to meet their requirements.
4) Since this would be the case of inter cast marriage, you have to ensure that your partner is not unstable if there is a break out of riots in the society and at the same time not influenced with the propagandas originated from the people having vested interests.
5) Both of you can go in for the blood check ups to ensure that both of you are in perfect health and are free from venerable disease including genetical disorders. This would eliminate your unnecessary worries once your deal for the marriage is finalised.

Though it is very nice if you think of a girl from a different religion, there may be many problems in your life because of this inter-region marriage. Both you and the girl should be strong and should be able to face the situation boldly.
From your post, I understand how strongly you are loving the girl. I wish that you should marry her and you should have a happy married life.
Initially, you and the girl sit together and discuss all possibilities and ascertain whether both of you are ready for marriage under any circumstances. As already you are sure that your parents will accept your proposal, tell them and ask them to convince the parents of the Girl.
The girl should tell her family that she will marry you only but not anybody else. She has to show her determination so that her family understand her deep low with you. If they agree, you can go ahead.
I think both of you are above 18 and not minors. So you both go for a registered marriage. Once your marriage is over the girl's family may also agree to the same immediately or after some time.

Rather convincing your parents, you should get convince yourself with your fiancé whether mutual understanding would be there. Because the different religion have different follow ups etc., In the initial stage of love it seems to be everything alright but later there are chances of misunderstandings, as for as I seeing personally.

An arranged marriage with consent from both sides is safe and the best. Mostly, the problem is not in intermarriages. The couples who are going to live together should have the tendency to give up with small fights and regrets.

Nobody can recommend how to convince the parents. Parents have their own emotional feelings because they brought up the girl for years more than the partner in love. They have their own plan for how to care for their children.

So, it will be better to think about marriage only if both parents accept this. Parents have enough experience on how their children going to live in their marriage life. Hence, parents are the best consultant in this and their judgment will be the true justice.

Nowadays, love marriages are very common. Especially in love marriages, there is no guarantee of religion and caste. There may be more chances that boys and girls belong to different communities. The most important thing is, that both of you should have a mutual understanding. Because both of you have to spend life together. Your first work is to notice the girl that she also loves you with heart or
just physical attraction. She is ready to bear up and down in life with you. In many cases, it is found that boys and girls start fighting over small issues after
marriages. At that time no one would be with you to solve the problem as in a love marriage generally, parents don't want to interfere. In such a situation your life would be hell. As far as parents are concerned, if both sides parents agree then no doubt your married life would be the happiest. So, at first, you talk to the girl's parents about the relationship and try to convince them. If they become agree then go ahead, otherwise you can go for registered marriage.