Meeting ex's gf My son's dad has this gf or f*** buddy idk but I know she's around my son.

Yes, I'd want to meet anyone that's around my children regularly.

If she's around your son then definitely yes

What would I even say?

I suggest something like "run" XD

Jokes on the side, I guess you can just be polite and see how the convo goes. Maybe ask her what she does in her life. She doesn't necessarily need to pay for your ex's mistakes, but I'm sure you'll pick the attitude straight away if there's any

Do you?

If they are going to be around my son, yes I would definitely want to meet them. I just don't let anyone around my son.