I would say something next session about my sense the sessions are ending 10-15 minutes early and hash out the session times/payment amounts, etc. to make sure my understanding of what I am paying for is correct. Sessions are different lengths therapist to therapist, client to client, insurance company to insurance company, agency to agency so it can be hard to know without asking your therapist specifically about you and her situation what exactly is going on. If you want to look around for a "better" deal, if that is important to you then I would discuss that with T too and then do whatever you decide.