How long was she in with the ram? Unless you just took her to the ram, or him to her, for only a day or 2, it is possible she came back in heat and bred on the next heat. And some of our cows don't udder until they drop the calf it seems and the heifers tend to udder up a week to a month ahead.
If she was in with the ram for 4 cycles, it is very possible you may have missed a later breeding. And trying to pin point it from today through Friday is like telling a pregnant woman she got pregnant on such and such a day and WILL have the baby from this day to that day... PERIOD....end of discussion....
NO mother nature does not work that way. The body will be ready when it is ready.
So, if she was 100 days on June 20th... that still makes her due starting around the 8-10th of Aug... so sounds like she is right about on schedule. If she is not a first time young ewe, then she might just not udder up too far ahead. Some just don't. But no sense in borrowing trouble. If she does not have much milk when she lambs, the lamb will only need the colostrum and they don't get a whole lot the first couple of times... That gives you time to plan for bottle feeding if necessary.
I had a yearling ewe this year that I didn't know she was bred and didn't get a bag until she had the lamb. I only realized she was bred when i saw the lamb with her lol. Hopefully you don't have to bottle feed.