ask her about herself, tell her the man she texted is your husband, confront her and tell her to stop.
after stopping the affair, confront your husband and ( be the boulder in this situation) don't let him feel any more powerful than he should feel, change the topic or just walk away.
if the worst comes then stay apart from him or call the cops if hits you. I wish you a safe future and hope you do the right/reasonable thing
many bad things can come from this kind of a situation, or he might give in and possibly tell you something like he didn't feel the love, or you weren't paying him any kind of attention. it might be a confusing situation, ut remember, he still cheated on you, that's if he did cheat on you.
it could still be a misunderstanding.
take matters into your own hands.