My father came with me to a few sessions with one of my Ts awhile back. It was for a very specific purpose, and my T and I discussed in detail how much info would be shared ahead of time, etc., and how the session would go. It was done for the purpose of making my life easier, not for him or because he had asked to come, if that makes sense. I wanted him to come so that my therapist could help explain some things to my father that had been going on with me at the time.
If you are not a minor (even if you are, you still have rights to your own confidential therapy, it's just that I know that parents can make things more difficult for you in this case) and if you don't think you would find it beneficial in any way, I really wouldn't suggest it. That is, don't allow her to come just because SHE wants to; it's your therapy!