Looks like foal movement. I've never foaled out a mare but I was there when my friends mare foaled out and there was a lot of foal movement that looked similar to that.
I'm just wondering how the vet missed it?! I personally wouldn't trust a vet after that, I mean, that's not a little baby if she's as far along as it sounds she is. I guess I'd still get her a check to be on the absolute safe side. Congrats and good luck!