My bf’s ex won’t stop bullying me and i don’t know what to do

I 17(f) and my bf 17(m) have currently been dating for 4 and a half months. Before we dated, he was in a long term relationship with his ex 18(f) for around 9 months. Now, while they dated, I knew of him but I was never friends with him or was even close to him at the time. It was only after him and his then gf broke up (now his ex) when we started getting close and eventually got together after some time. Him and his ex have been broken up for months now but she has recently been talking shit about me in my own class. I have a class with my friends at the end of the day that used to be my favorite and my bf’s ex had an entirely different class however, now that it’s the end of the year, she skips her class everyday to hangout in my class.

I’ve never talked to her (before or after the breakup) because frankly, she’s a horrible person and I wouldn’t want to be friends with her but she has now been starting problems with me. Her friend sits right beside me in class and I used to be somewhat friends with her but after recent events, I no longer agree with that. Because her friend sits right next to me, when she hangs out in my class, she is two seats away from me, meaning that I can hear the conversations her and her friend have.

Now, at the beginning there was no problem, we both minded our business and didn’t acknowledge the other, but after some time, she started to bully and berate me. It started small at first, just little things here or there but I brushed them off until most recently, she’s been having full on conversations about me and doesn’t even try to hide the fact that she is talking about me. My bf has told me not to acknowledge it because it’s attention that she wants but after a recent event, I know I can no longer let these things slide. I didn’t mind when it was just words at first because they were stupid insults like “why does she look like that?” “why does she wear that?” “why is he even dating her?” (in reference to my bf choosing to date me now). Recently, her and her friend were putting on perfume and tried to “secretly” spray me while snickering and talking about how it now smelled better. I am one who takes pride in my personal hygiene and I always make sure I never smell because of it, so I know that this was a lie and just something that they were doing to get under my skin.

My bf keeps telling me to let it slide but recently said that if I do choose to say something or do something about it, he will back me up on it. After today, i’ve decided i can no longer stay silent and want to confront her, although there is only a week left of school so I don’t know if it’s worth it. I’m usually not one to speak up but in this case, I desperately want to stand up for myself. I’m at crossroads with my decision. Should i do something or not? And if so, what should I do?