I'm not sure what capability the Dark One would have to rescue her from the twisted dimension of the Finns, so I'm going to approach it from another direction.

What if Lanfear's body and soul is still being held prisoner, but her mind was pulled into a new host body?

This would account for the difference in channeling strength, the possibility that her memories remain but not the other elements that are present in ones' soul, and her lack of anger regarding her lost strength. Lanfear's personality type makes it noticeable that she would at least comment on her lost strength in more ways than she has currently. Perhaps her reward for serving the Dark One well would be the capability to retrieve her lost body and soul? Perhaps part of her punishment is to be put into a body in such a way that everything she was most proud of has been stripped away?