I'm not saying Dora's like this at all, but I have seen people do that, essentially demonize a decent ex to justify dumping them. Especially when the dumper is seriously in the wrong, for example they cheated or something like that. It's often easier to blame the other person than own up to their own mistakes.
Dora's at least trying to own up to her part in the breakup-but the aftermath of her first therapy session shows she's got a ways to go. EDIT: you're right Is It Cold, we've never heard Dora mention how she deals with exes, but the fact that she doesn't talk about them much, what her brother said about the kind of guys they were, along with us never having seen any of them, leads me to think she most likely is NOT friends with any of them, and would probably be happy to never see any of them again.