Actually McMann has fought a couple of Judo fighters but they couldn't do anything to her. Then again they weren't at the level of Ronda. She also has found herself in quite a few submissions, but again not at the level of Ronda. The problem with McMann at this point is she is like when the UFC first started and you had guys like Coleman who knew enough about subs to power out of them. Well Ronda is just after that level. She would get destroyed by any of the mens 135'ers not just because she is a woman but because they are WAY more well rounded than she is. At this time Ronda is way more well rounded and what she is versed in she is extremely well versed.
Long story short, in round 1 I expect McMann to probably get a TD and even get out of a sub by powering out. But she can't power out forever and we found out against Tate that Ronda can throw them forever.
The Problem with McMann is that her best hope at beating Ronda is striking and her striking might not be up to the challenge.
Ive seen most of her fights, she's not going to be out preformed athletically or at least IMO thats not going to be a factor. I think she's going to get waffle stomped with a superior skill-set, Ronda has more ways to win and she's actively seeking to stop the fight at all times.
Thats not to say its impossible for McMann to win, Ronda has made mistakes in past fights but nobody has been able to capitalize on them so maybe McMann can but I doubt it.