Friend problems... Help??

So my best friend has really done things that are frankly pissing me off. We are juniors this year. I've been in a committed relationship for the past couple years, but she's kept all guys at just a friend status. Well more than friends. Lately its like all she does is beg for boys attention. Wither its sexting them, flirting all the time, letting them touch her, or wearing her cloths so her VS underwear can be very visible, she toys with all of them and its getting frustrating. They all view her as a sex object now, and her reputation is starting to fall apart. Then she comes to to me to answer why nobody takes her seriously and asks me to put rumors about her to rest that are entirely true. How do I get her out of this without hurting her feelings?