As always: The only one who should tell her to stop flirting with him is your boyfriend. If you do it, you'll only be seen as insecure of your relationship and overly jealous of other women.
Also If you can't be sure of your boyfriend staying faithfull against her advances: Why are you still with him?
Ignore this bullshit and keep some distance to that 'friend' who flirts with your boyfriend due to her 'personality'.
We called the first girl my college room mate dated “Bitey” because of her oral technique. We don't remember her name. Hope she got better.
As always: The only one who should tell her to stop flirting with him is your boyfriend. If you do it, you'll only be seen as insecure of your relationship and overly jealous of other women.
Also If you can't be sure of your boyfriend staying faithfull against her advances: Why are you still with him?
Ignore this bullshit and keep some distance to that 'friend' who flirts with your boyfriend due to her 'personality'.
I think you might reach out to some domestic violence support groups and explore some of their local resources you can connect with in your area.