I’m going to my first massage. When do I tip the masseuse? Like when she’s done with my massage she will have to leave the room so I can change. When do I tip her?

Assuming the massage is taking place at a business, you would typically “check out” at the front desk even if you’ve prepaid online and can tip then. If it’s just an individual I would pay her after you’ve gotten dressed at the end—presumably she will have to escort you out. Enjoy!