If you asked for her on the phone and she came, I don't think who answered the phone is a concern or matters. We all have friends, relatives, partners, etc. in and out of our homes but they are not part of a relationship with another unless we make it so? Your therapist cannot know the exact moment you are going to call and she might have been in the bad? It is like calling an office, you do not care who answers the phone, you just want to talk to the person you are interested in.