"When I move my speech into a higher vocal range, I don't feel female... I feel like a kid,..."
Well, there is a sort of brain-mapping that relies on our voice resonance in our skull. Maybe the therapist told you this already. It is this mapping that will need some time to change i.e. to feel OK, and not childish when using the higher register.
After a while you will feel this higher register, mostly only 1/2 octave, to be quite alright. It is yet another challenge to maintain it!
I found that with short hellos and good buys, and short light chit-chat, it comes naturally. In fact the more femme I feel, the more it simply is a need to express myself in those higher notes. Any female will do much the same by the way.
The challenge comes when you need to get more authoritative in e.g. calling a dog to order, or getting into some longer and more serious kind of discussions about anything.
In all such cases my voice will drop - sometimes REALLY too much, so that at least I notice it after a short while.
Funny thing is... once you set the 'pace' started off high, on a femme 'welcome note' - very often one's voice dropping in pitch, then is hardly noticed by whom one speaks to.