I was outside thinking about the Rambam and it occurred to me that what I had written to answer a question in the Rambam was not well thought out. The wife in Ketubot page 9 is not going מפטור לפטור. She is saying one thing along--that she was a virgin. That has nothing to do with the sugia [subject] I brought up about מפטור לפטור. It is a simple case of a Migo. My  question is simple. Let's believe her when she says she was a virgin because she could have said משארסתמי נאנסתי. To answer this has not to do with that Rambam about a lender that changes his statement from I never borrowed to I borrowed but paid back. So why do we not believe her? She has a חזקה, חזקת הגוף שבתולה הייתה and a migo. He has two חזקות, חזקת ממון וחזקה אין אדם טורח הסעודה ומפסידה. So one חזקה cancels the other. And we are left with a מיגו against a חזקה, ואין אומרים מיגו להוציא מחזקת ממון. So teh only question here is to תוספות in בבא מציעא ק''י ע''א to one מאן דאמר that a מיגו can take out from a חזקה