It's difficult to think about what could really happen to Betty Ross cause the clues are very weird. What I do belive is that if she doesn't scape with someone or cause she was tierd of her life, her kidnnaper mut had been someone who she knew because otherwise there had be any clue to think that an stranger enter on the house without letting any mark an the doors or windows.
Probably she wanted to sart a new life because she wasn't happy or she was in a very complicated situation at her house, so she diced that the best option was to ran away, maybe with some kind of lover.