Well, we can still watch her -- even if we're waiting for her to come into heat. LOL Sure is strange, though. She doesn't look like a mare that's overweight, and so might have that belly, and in some pictures it seems like there is no belly. I think I'd still be watching her, at least until the end of the month!
I had a mare (new to me at the beginning of breeding season the summer before) who daily had me confused for months. One day I'd think she was pregnant -- and she looked pregnant -- and the next day I'd just scratch my head and decide she wasn't pregnant. This went on for at least 3 months. Then I decided she certainly wasn't pregnant -- she had no belly and no udder, and I put her in with some other ladies. I was very sad when later that evening I went out to feed and there lay her baby still in the sack on the ground, with her standing guard. Very sad, but made me realize that these ladies can really fool you right up to the last minute. She looked exactly the same as when I left her in the morning except now she had a full udder and a lost little one.
So, I guess I'd just watch until she comes into heat again. We've got nothing better to do than help you watch while we all wait.