I think maybe they were simply ill-matched. They produced some lovely performances, but she did seem quite on edge, and not particularly enjoying herself.
I'm not defending him but there's possibly fault on both sides. She has a difficult home situation, I gather, and maybe that played into whatever happened too. I remember the first night just as they were about to run up to the Clauditorium, I felt that Gio was steeling himself as if - 'here we go, this is the next bit I have to get through'. I posted about it here at the time, so maybe his heart wasn't in it either.
If say Angela S was with Gio, she seemed to be the type who would say nope, I have had enough. But not for anything would I have wished Angela to be with anyone but Carlos.