She isn’t flirting, the guy is. She can easily block and ignore him forever and that is her fault. The rest of the blame goes to the husband, which is like 90%.
It’s his job to keep his wife satisfied. It’s not just a one way street. A husband doesn’t need his wife to be feeling good to get satisfied. Unfortunately it doesn’t work the same the other way around.
If she wants to be satisfied, then it is his DUTY to do it. He can bring home money, food and take care of the kids all he wants. That’s also his DUTY. But you cannot neglect issues like these because he’s doing his job at other things in married life.