From your description, it’s pretty clear she is having an existential crisis and is probably very depressed. I have been there with my daughter. There are lots of crappy, unqualified therapists out there, I am sorry to say, but there are also some very good ones. Keep trying until you find one in the latter category. We searched for one with experience in treating gifted children and it made all the difference.
Don’t apply to college for her (illegal here in the states). College is step 2. Step 1 is getting her well.