If she's been swollen for "about a week", then she could be coming into the flagging stage. Or obviously she is, since they've tied. Maybe her cycle started before you noticed it and you missed the heavier bleeding and/or she's a light bleeder. Or maybe she has been keeping herself extra clean and you just didn't see the bleeding. It does get much lighter colored when it gets to the actual breeding time.
Or, and I don't know too much about this, but could she be having a false heat? Not sure what that entails, but these are the things that come to my mind on what Bebe (and you) have been experiancing. Since they have had a couple of successful ties, you'll know in about 63 days whether she was in heat or not
Good luck to you. Maybe someone else will have better and/or other answers for you.