either way
whether he's cheating or not
he's clearly entertaining that outside bullshit which in turn undermines the relationship any way you look at it.
Love or lust will and has made fools of the best of us. As someone who's been exactly where she is, she needs to RUN as far as she can in the opposite direction. Like yesterday. Because no matter what she says, if he's doing this now and she allows it it's only guaranteed to get worse.