C.B.
He really needs to talk with her and let her know that as much as he loves you, he will never stop loving her. He also needs to address the issues of her jealousy and what she is doing and let her know it's not ok. Calling him honey bunny and saying she wants to marry him is (in this situation) over the line with how a daughter should act with her dad. Have you tried spending time with her just you and her? And having him spending one on one time with her? I'm not if the exwife is in the picture or would be willing to do this but maybe she could say something to her daughter along the lines of "It's ok to like (your name)." Or if that's not possible, maybe your husband could. She may be feeling guilty for liking you.
When we adopted our children, they were very attached to their foster mom. She had to give them permission several times (one of my daughters in particular) that it was OK to love us and she wanted her to love us. She felt like she was betraying her foster mom if she gave in and loved me.