If the demon speaking through Gage at the end is to be believed, slept with all her husband's friends. It's debatable whether this is true or not. On one hand, the demon said the truth about people's secrets before. On the other hand, what he said about Norma was pretty outlandish, and he said it to make Jud angry and lose control. It's possible that there was truth in it, but the demon exaggerated. Jud is guilty of infidelity himself, so it's definitely something he would be sensitive to and lash out. Notably, Timmy Baterman said nothing of it given that he gleefully told Alan Purinton of his own wife's infidelity, it would suggest demon Gage is lying about Norma, unless she only cheated after Timmy Baterman's second death.