phi mu is harassing my little sister..help

my sister had to drop out of school because of issues she had, including within phi mu with the way they treated her as a "sister" and after she dropped she wasnt bothered. she had a picture of her in a white dress and some other girls in another picture from their pledging last semester. a couple weeks ago she got rude, harassing messages from phi mu girls (specifically on the exec board) until she deleted any evidence of phi mu from her social media so i was wondering since my sister wants to stay anon since she has stuff to deal with already, is there any way she can tell CU Boulder/Phi Mu HQ about this anonymously?? this should not happen anywhere or to anyone. they even made fun of her for not being rich enough to pay her bills, which is part of why she had to drop.