my friend flirts with every guy

she will flirt with every guy that we talk to or see that she thinks is cute which is fine as long as it's not my brother and his friends 🙄 i invite her to the beach house and she flirts with my brothers friend and he flirts back. it ruined the couple days we were there and i told her to stop but she claimed she didn't know she was flirting (we r juniors in high school) late at night we have a fire on the beach with the guys and us two and we were drinking and they were smoking cigars and my friend and this guy r sharing drinks and cigars and went down to the beach together and i just realized that i can't ever bring her to any fam events or anywhere where my brother and his friends r. also good by my future parties and bringing her to my brothers friends parties. this isn't me being jealous this just me being annoyed as i can't take her most places now. and all my bros friends r like my brothers so it's just so weird and ugh. she even has a streak with a different one of my bros friends. he's called her cute and she flirts back "without even knowing" but its like dude lose the streaks these guys r in college anyways and just want to get into ur pants. she pretends to be clueless