13 year old sex & STI

So... my niece is 13, sexually active, she's confessed to being with 4 guys so far... and just found out she has Chlamydia. My sister doesn't know what to do anymore. She's has to quit work because she can't trust leaving her home alone. They've nailed her window shut just to discover she was able to get those out. My sister feels that at this point she can't stop her, so she's just going to provide condoms and educate her to be safer. What else can be done?? She's already on birth control. 😩