Commentary for Kiddushin 126:13

The Talmud rejects R. Assi’s own difficulty on himself. The woman is simply not believed enough to cause her or the one she sleeps with to be stoned based on her words. There is different reasoning for this issue than there is for the issue of allowing her to marry someone who says she was betrothed to him. It is not that we believe her more than we believe the father. The issue is that we fear she is colluding, as we learned in yesterday’s section.