Well, if it is true what many of us believe happened that night, she clearly wasn't going to put up with it any longer, and was about to leave him. The problem with these types of Jeckyll and Hyde characters is that you are drawn in by them because of their nice soft, caring side and often their wit and intelligence (not sure that applies in OP's case .. but Reeva did mention him being clever once, and she seemed to be very struck by him because of that), and then when they start getting nasty, you can't quite believe it, so you keep on giving them the benefit of the doubt until such time as you realise that you're not imagining it, and this is what they are really like. But give her some credit, she was only with him for 3 months and it seems she was most likely leaving him that night because she'd had enough.
This is one of the things people in general need to learn about abusive relationships and how you can't just say 'why didn't she leave him' .. there are all sorts of reasons why women don't, or are not able to (especially if they are not financially independent) .. and imo, the question shouldn't even need to be asked, not if people fully understand these types of relationships.
It wasn't even 3 months really, wasn't someone going to try and do a time chart to see just how much time they had actually spent together, what with both their careers, traveling, holidays, living in different towns, etc?