1. IF Girl is Major age, and IF physical relations were with "Mutual Consent", THEN no offence is attracted /applciable even IF false promise was made. This has been upheld by several HC /SC judgments.
The questrion lacks clarity and precision. we cxannot assume and presume facts to give a legal advice. the party must come out with some crucial facts. What this question directs is some thing like a "Sex Pact". as said by supreme court
If there is a promise of marriage and the same is not met with, the girl can file this as a case of Rape. There have been numerous judgements provided by the Courts regarding the same. However, if it is with consent and the marriage proposal is fulfilled, no charges will be attracted. Please remeber that the relationship you shared if it is based on a false promise, it is then considered Rape. You may refer to these articles -