ANSWER:
She is sinful for betraying her husband and talking to non-mahram men behind her husband’s back!
She must break off all communication with him by blocking his number and repent to Allah while showing deep remorse and sincerity for having anything to do with him in the first place while making a lot of Dua in the sujood of her prayers for Allah to conceal her sin. She must not tell a single soul about this. If he decides to kill himself, he will end up in hell where he belongs. But if she doesn’t cut communications with him totally, she will end up in hell with him!