Child anxiety question

[Blockhead59]

My daughter has recently been seeing a therapist for her extreme anxiety, which she's had since she was at least 4 years old. I wouldn't put her on anything until she was at least 16, and then we spent most time going to biofeedback, therapists, massages, etc. 

Naturally, I asked my daughter, what I had done wrong to mess her up, as it's always thee mother's fault

My daughter said that her therapist told her that I should have let her stay in situations (like sleepovers) when she called and asked to come home, because it would have helped her build up a 'resistance" of sorts to her anxiety.

To my mind, leaving my daughter at someone's house, when she wanted to come home would have been cruel, to say the least. 

We talked about some of the times she called me and said she wanted to come home, and I can't find any justification (in my head) for leaving a child who's scared and somewhere she or he doesn't want to be. 

Maybe I'm wrong. Maybe I was too overprotective. But, personally, I don't agree with this method of handling a child who wants to leave another's house. 

Any thoughts would be helpful to me as I try to process this logic. It just doesn't make sense to me. 

Thanks and have a great day!