Martha listened to his explanations without comment, letting him say his piece. She hadn't doubted that there were similarities between Rose and Marian, everyone had certain types they were attracted to, some traits that would remain the same. But it was making sure that Rose wasn't simply some Marian substitute to him. And the honesty in his words was reassuring.
So she nodded with a small smile. "Whatever this is between you two, whatever it has the potential to be, at least you're both aware of things, like Marian, like the Doctor." There was a slight hesitation. Martha was never quite sure what to say in regards to the Doctor. Her own feelings for him were complicated. Oh he was wonderful, brilliant, and for a while she had thought she had loved him. But he was also fire and he had burned her. Not intentionally, but still. "I do know Rose well enough to know she never just replaces someone. Yes, she loved the Doctor, but he's gone. And she's really not the type to just drop someone the instant he comes back." Even with Mickey, once Rose had made her choice, she stayed with it.
"Everyone has a past and it helps make them who they are. It's what we do with that that shows the kind of people we are." She offered a rueful smile and toyed with her glass of wine. "I know you were there for her, after I, you know, died and everything. And I wanted to say thank you for that. And yes, you do get points for not trying to kill Robin and Marian. Well done."