Really none of that sounds like a weird relationship to me. It just sounds like... basic companionship. She was mildly annoyed that Twelve didn't visit in two weeks because - who wouldn't be? At least given how often they usually hang out. And, I never noticed at any point that she really "ditched" Twelve. She just wanted to go on a few dates. And when was she upset that he wanted to do something without her? That I don't remember at all.