Let me say that I am 99% sure there is NC between her and her AP
I would be inclined to ask you, how are you 99% sure if you, by your own statement, never check up on her? She has a looooong history of repeatedly cheating on you, and you never verify? Listen, she has lost her ability to be blindly trusted because she has destroyed that trust multiple times over a several years span up to and including this year. She has proven she's not trustworthy, and the only way you should consider trusting her is by seeing proof of her trustworthiness each and every time you check up on her and things are as they should be. Period. By offering her blind trust immediately after the umpteenth DDay, you are simply sitting in the corner waiting for another DDay to happen.
(Putting the 2x4 down, sorry)