Well, it's been firmly established that Marten is okay with Tai and Dora dating. And beyond some mild anoyance that Tai is coming to him for advice about his ex, he seems to be okay with giving Tai the owners manual. The real potential issues now are when Dora finds out about Tai going to Marten for advice about her. She might even be okay with it, but it will lead to questions as to why Tai went to Marten and not another friend. And if Tai gives her the same answer she gave Marten, well, it has the potential to set off Dora's issues. Dora obsessed over a couple of girls Marten dated back in High School that he "still had feelings for". Therapy or not, dealing with her issues or not, I have trouble seeing Dora
not reacting badly to the knowledge that Tai has four or five "exes" she can't really talk to any more. Plus there was the physics professor she had at least a casual relationship with. And who ever else was in her circle of bang buddies that we don't know about. All of which were recent. (How recent is up for debate, given in universe time is an unknown to us.)
And as Mad points out, there is always Bailey.
Something I noticed - Dora got away from butt-grabbing for quite some time in the strip.
Maybe she was begining to distance herself in the relationship when she "sensed" things going pear shaped.