Hi Claritytoo!

Your biological sister phoned you at your therapy session. Your sister alter usually talks to your biological sister, but you had to do that. And I guess you did not have conversations in front of your T. Or did your T notice anything?

Does your T know you have this sister alter? If she does, you could ask her if you changed to an alter or not during a session. You are seeing a psychotherapist, correct?

If your T knows you have a sister alters or any alter, then your T should not freak out.