Maybe it's not that what you want is unreasonable but that you're trying to get something from therapy that can only come from working on a relationship in the outside world, like with a partner, as you alluded to wanting a mother/partner/friend/sister. That your attachment needs need to be met through a more regular, typical attachment.

There's something very deeply satisfying about having a partner or very close, deep female relationships like that which can be replicated in therapy, but only an hour at a time, occasionally.

It's like prostitution in one sense, emotional prostitution, that surrogacy.

I don't mean that in an offensive way or as a slur. I think escorts do respectable work and important, but that they act as more of a bridge, if anything, a temporary substitute, not a partner.