It re-emerges from time to time for my dd10 - stress is one factor, and I'm thinking now that she's almost 11 (and it's re-emerging :)) that hormones might be another factor.
I sorta wish I could borrow your dd for a day and let her hang out with my dd in the backyard - my dd is basically driving the rest of us a little nuts at the moment, but she clearly needs her space to be wiggly and wild and I'm guessing she wishes the rest of us in her family were just a little bit more sensory in nature at times!
Do you think you need the OT or could you use some outlets for a while to help deal with it? We used to send our dd outside to swing swing swing when she was younger; since your dd likes to swing, could you make that a required part of her day after school? Can you let her go outside and play for 30 minutes after school every day? Can you get her a necklace or bracelet or one of the pencil-topper things to chew on?
FWIW my dd went to OT for sensory when she was 4-5 years old, but I'm not so sure it would work as well now at 10, whereas when she was younger getting her to do active things at home, or in after-school activities etc was a bit more difficult than it is now, which is why I'm thinking maybe this is something you could possibly approach outside of OT.
Best wishes,
polarbear