well for starters if she talks about him alot theres a chance
she still likes him. also if she still has any pictures up of him,
talks on the phone with him alot, they still hangout somtimes. but
if she totally doesnt even pay attention to him or talk to him
theres a big chace she doesnt liek him but you have to be able to
trust her because that's one of thekeys to a healthy
She may go out of her way to talk about him or include him in your
plans. When your out if you see him she may get flustered or gitty
around him. Why not just ask her for the truth so you don't have to
waste time on someone who isn't respecting you.
I would ask her directly, wait and listen to her response. If she
becomes defensive or angry, be careful. If she simply tells you she
does not like him anymore, I'd believe her. As others wrote trust
is key in any relationship, as is communication.