I think Bristol is like her dad and just doesn't feel comfortable with PDA. Although Todd did say he'd like to learn to dance. (Might come in handy in the WH).
She says they are friends. (Good place to start.) She has had to trust him to allow him to touch her in all the places the dancing required. She said he is very professional. Think of the talk if she didn't make those statements.
I know I have seen him more and more get her to have some input in the Dance Routine, and she seems to let him into her space.
I would love to see her in a relationship with Mark, but I think it is too early. It would be nice if they could stay close, he is an only child and they make a cute couple. They are the same height until she wears heels. LOL!