Last Tuesday she told me she has a thing for my mate

Last Tuesday she told me she has a thing for my mate. Just like that, in the car coming home from her sister's in Drumcondra. I nearly missed the turn at the lights. Like what am I supposed to do with that information tbh. We're together 6 years living in Stoneybatter in a one bed above the chipper, smell of grease comes up the stairs every evening around half six. I'm 32 she's 30, I'm in IT she does HR. The mate is my friend from college, knows me 12 years, comes round for the match every other Sunday. She said it's just a thought, nothing happened, won't happen, but she wanted me to know because she said keeping it inside felt worse than saying it. Now I can't look at him the same and she keeps asking am I grand. I'm not grand. Tá's agam she meant well but I don't know what to do with this. Do I tell him? Do I pretend she never said it? Do I ask her if she actually wants something to happen freisin or is this just honesty for honesty's sake.