First you are requested to click on applaud just left hand side of my post.
The question of Running away from a relationship does not arise at all. Staying together does not mean a live in relation. If so, then two boys staying together in a rented room tantamount to leading a GAY relationship. This isn't so cause the nature of their behaviour and acting implied that they are friends. So, same rules applies in your situation. One boy and a girl can stay together as a friend, that does not mean that they are in a live in relationship until and unless both of them agreed to. Staying together for few months does not tantamount to the definition of husband wife. Moreover, if there is no consummation in their relationship, then from no square they are deemed to be husband wife.
Answer to query no .4
The boy can file a case against her at any point of time but that will not be tenable in the eye of law. As per your situation the boy has no evidence. Evidence is an optimistic nor illusive or imaginary. Mere photos of holding hands is not an evidence to prove of a husband wife relationship. Further if such evidence is brought then that evidence is required to be challenge strongly with cross examination or from forensic department.
What precaution you are asking? when there is no marriage tie up or prove of live in relationship earlier. Moreover, when she denied about the live in relationship with that boy. Though there is no precautionary measure in your circumstances.
Basically, if she denied that she had ever been in relationship under the definition of husband wife then no law or ex boyfriend will cause any harm or cause obstruction for her marriage. In the eye of law is virgin and she did no wrong for staying with a friend for few month as a room partner. It is we, the low mentality people think nasty that if a boy and girl spend a night or stay together in a room, then the girl is no more deem to be virgin and we dont trust her. SOOCH BADLO...TABHI TOH INDIA AGEY BADEGA...