Why doesn't she want to go?

It could be helpful to approach the issue as your trying to understand why she doesn't want to go rather than your trying to persuade her to go. Because ultimately it does need to be her decision and therapy won't be beneficial if she really doesn't want to be there.

Of course it might be the case that her concerns can be addressed and she will decide to go after all. But if she doesn't feel heard (if she feels made to go) then it probably won't be very productive.