Hi Flipper,
What a sad situation. And yet there is some good in it.
As others have already said, she is having some form of communication with you and I'm sure you're grateful for that! :)
As far I can see there are 2 routes you can take.
1.) Say something like "You're probably never going to leave and I'm probably never going to go back, so let's just get our relationship to the best it can be within those parameters." Or words to that affect. I spoke to a counsellor about saying something like that to my still-in family. He seemed to think it was a good idea. I did say those words to a sibling and it worked very well. Definitely took the sting and her suspicious feelings out of it. And did improve the relationship.
2.) Belief what Steve Hassan says. She will get out of the cult, its only a matter of how soon and how easily. To that end, consider doing what he recommends in the book and prepare an SIA with her. Do all the necessary prep work and then try and spring her. A hard slog but with the best possible outcome as the potential result. Depending on your finances, it may be worth considering contacting Steve himself. His book doesn't really cover the eventuality you and I are in, ie trying to release people from the bonds that were once ours also. So his personal involvement may be the added ooomph you need.
All the best in whatever you decide.
Keep us posted!