She needs to just cut her husband off from intercourse. Just let him eat her pussy or jerk off on her. That's what my wife did to me in 2017. It's just easier.
The husband really loves her though. No he can't compete sexually anymore but that's what her boyfriends are for. He tries so hard to reclaim her after she's been fucked but to no avail. I understand the frustration and angst he feels.