How would you approach your close friend about flirting with your boyfriend or girlfriend?

If you had a friend that always called you their bff, that you met because you use to date their brother or sister...and then you broke up with their brother or sister and started dating someone new later on. And then you always have had people come to you about this person flirting with your new man or girl. But you kind of noticed it but never spoke up about it. Its been going on for at least 2 years and you finally getting pissed about and want to confront the B%*%26amp;! about it, What would you say? What do you say? I mean your man or girl try to ignore her or him but this person is pretty consistent.How would you approach your close friend about flirting with your boyfriend or girlfriend?
unfortunately, its not your job to say anything. You won't change her. Either accept who she is, or stop being her friend. (I would stop being her friend, because it is blatant disrespect.) BUT, it is your boyfriend's job to tell her to stop. And he should know to do it without you telling him. You can tell him if you have to.