David are you sure she went to Cambridge to try to put it back together? There may be other reason's that she went to Cambridge to see him/his lifestyle.
Well fine, you can speculate about why she went back there but the essential point was that she wasn't sufficiently afraid of him to deter her from going back there.
I don't really see anything that leads you to think that spousal abuse is the cause for termination of their relationship in August of 1961. I agree that she had some sense of urgency to return to the U S from Kenya but the source of that urgency is speculative.