The mounting is definitely a dominance thing with Chloe. But I sense she is also feeling safe by being on leash with you around for protection...sounds like a bravado thing to me. If she's off leash when you meet another dog, watch till you see her tryng to mount and turn in the opposite direction and walk away, she'll forget the mounting and come running...but don't turn around to peek, walk away fast. At home I would leave the room when she starts this and let the other dogs show her some manners. I think the fact that you always intervene makes her feel safe so leave the room and go into another room and shut the door...she'll soon be looking for you. We see dogs like that at training classes all the time, so brave when the owner is on the other end of the leash but running away if off leash and owner walking away.