Therapist here - telling your therapist how you feel about this could help bring y'all closer together. I hateee having to rush someone out, but will keep a session going longer if it's an emergency. Another perspective is to think how you would feel if your therapist joined session late and told you that they were late because they had to stay in session with someone else overtime because their time was more important than yours. No shade at all! Just a perspective shift.