I'm going to tell my wife to cut contact with an old female friend of his
What reason do you have for that?
She's spreading rumors about the family.
You are smart to want to stay away from malicious gossipers like her. But make sure it is her spreading the rumors first.
I knew I can rely on you.
Have you and your wife discussed her friends gossip? If you have proof it was that friend, you are very smart to bring it to your wives attention.