If that explanation doesn't resound with you, try this on for size.

I've known cases where therapists have done a 180 and left the client baffled. After a big old rupture and lots of tears, the therapist admits a colleague or supervisor gave them feedback that made them rethink their strategy. The therapist starts doubting herself and questioning if what she's doing is therapeutic or if she's harming the client in some way. Therapist ultimately panics and, in her haste to correct course, harms the client. This seems to be a common story when therapists change boundaries seemingly out of the blue from the client's perspective.

It sounds like a narrative where she's still looking out for your best interests (or thinks she is) feels more true to you. I can't recall an instance of the above scenario where the therapist just terminated all contact (at least not before trying to repair the rupture), but since she was never going to be your permanent therapist, perhaps this is what made sense to her at the time.

That could even match up with your feeling about the own two feet thing. I don't think it would make sense if she just came up with that herself since you say that's never been an issue. However, I could see a supervisor telling her she was holding you back or something.

Idk, just more ideas about what may have happened.