If she gives you the " I want us to be friends,you're like a brother to me, and making JEHOVAH HAPPY ( not you ) is very important to me..." line, I'd bail. Been there,done that, and it's been an enormous source of frustration over the years.
I'd continue to try to persuade her. Try not to be too pushy though. Just point out your view of things. If anything,she's been taught to resist all other literature,belifes,etc. They're wrong and bad. Just be subtle about it, and I think you'll make some leeway. If she's developed pretty good friendships with sisters....surely she has mentioned you to them, and they're probably trying to tell her to either convert you or leave you alone depending on how she may have described your relationship to them.