The main purpose being her interactions with Herid Fel and determining how to deal with the DO, which we'll find out in this final book.

Her secondary purpose was her unfaltering faith in Rand, even through his progressively darker period. Her belief in Rand as a savior was something that, I think, at least subconsciously helped him recover his faith in humanity.

With that said, she'll still continue to serve as support for Rand, and she's still good for short-term warnings of potential enemies, based on her Viewings. She can see threats, people who deal with the OP. She may give warning for a disguised Forsaken.