I'm so sorry your question got missed.
How was her incision? Was it swollen or reddened at all around the stitches, and did it start healing properly?
It's possible there could be some fluid build up where the incision was, or the lower part of it, and that might be causing her 2 lower teats to become too firm (swollen?) When she went for her post-surgical check, did the vet notice this or mention it? Or was it not there then?
My feeling is that you should call the vet who did the surgery and discuss it with him/her. They are usually happy to answer any questions you may have post-op. You may have to take her in to be examined.