Absolutely not and he will wear her down and sleep with her.
Wear her down? Or she decides to sleep with him, cause she is an adult?
OP some men do. But if it's already got this far, then it's still cheating. He is still lying to his partner, hiding things, deceiving her, putting his jollies in front of the person he is meant to love. For most people thats the part of cheating that people cant love past. Not the sex itself.
So she is still involved with a selfish dickhead.
He may just enjoy the attention and have no plans to sleep with your friend or leave his partner. I have known quite a few men and women who dont think is wrong. Even while they are deleting texts and sneaking off to reply.
Or he may shag your friend and come up with a long line of excuses as to why he cant leave yet while bullshitting promising he will leave one day
Maybe he will leave his partner and they will live happily ever after, while somewhere in the back of her mind she wonders if he is deleting texts from his new ego stroker.
Who knows....but if she is the type to get involved with an attached man, she deserves everything that is coming her way.