She doesn't seem to look much bigger to me, her muscles near her tail are soft and jiggly and her stomach was gurgling a making sloshing sounds quite a bit - BUT I'm no expert that's for sure.
I just found out one of the four mares foaled over the weekend. If I'm not mistaken there was Ella, two others and a fourth mare that were all bred around the same time. The other two haven't foaled yet, so Ella seems to be on scheduled.
Here are some pictures I took Sunday: