Left to my own devices, my instinct would be to cut back on OT, CBT, or social skills rather than on playdates... but the problem with doing so is that her school knows that DD is receiving these services, which makes them more prepared to work through any rough patches (as she's working on those issues outside of school).
My instincts on this situation are in agreement with yours. Play is a wonderful and highly-valuable component in child development, so that needs to be protected. And it doesn't sound like your DD is getting much value from the professional services at all. Cutting those out and letting your DD have some downtime before bed could make all the difference in the world in her behavior.
As for the school... if they already know you've sought professional services for your DD... is there any reason to tell them you've stopped?
