Your question though very brief, raises a very big question of law. The question here is not about marriage but about the consent of the girl in doing all the acts as demanded/asked by the boy. The acts may include spending money on the boy, going out with him, spending time with him, having s*xual relations with him etc etc.
It is very important to note that it does not matter how hard a boy tries to pursuade a girl, she would only succumb/agree when she herself finds a good future with the boy. Without that no girl would agree.
Now coming back to your question, going to police may/may not get the girl married to the boy, but a criminal case could easily be filed against the boy and police would harrass him unendingly and would extort heavy money from him under the threat of the FIR etc.
It is the maturity and foresight of the girl to understand if she would be happy with a boy who marries her in the fear of police case etc. It is again the maturity and understanding of the girl if she agreed to do everything with the boy with her own consent and will or she was forced into it. I feel it isnt a case where the girl didnt had any choice to say "No" but she opted to say "Yes" on her own decision.
Anyways, it is a case of cheating if after promising marriage, the boy does not marries the girl, if he did not had any intention starting from the beginning. It is well settled in the law that if the age of the girl is such that she can be easily fooled and she can be lured into fradulent promises, then she deserves protection. If there has been s*xual intercourse within this relationship, then even a case under S.376IPC (Rape) can be filed by the girl against the boy.
It is the maturity of the girl who should decide if she was forced into this relation and she did everything only because the boy said so, or she also desired it. If it is a case thas girl also desired to enjoy the company of the boy, then there is no case made out and on human grounds the girl should rethink and should not file any case against the boy. False case may send the boy in jail and he may suffer but would be girl gain anything? Just revenge is your criteria? Or you want to extort money from him? If yes, then go ahead and file a false case.
My personal understanding in such cases says, 99% cases involve free and voluntary involvement of the girl and at last when she wakes up to reality she feels that she has done something wrong, she just puts the blame on the boy.
Choice is your!