Some mares are tricky and will only give you a couple signs. Some mares will act like they are in labor and be completely normal the next day. I'd say keep her on watch until you can get the vet out.
I think this is a very good idea. Horses are built to be on the move, and cooping a horse up in its stall with no exercise can be detrimental to their health. I think it would be very smart to move her to an area she can spend a bit of time roaming around intoday i took her for a 30 minute walk. is that decent enough. and since our pastures have very minimal grass. we are debatign switching the other horses over to a pasture with more grass and giving her run of the main one for the day. so she can stretch her legs out.