<human>: Can you provide a brief rundown of the text in within 3 sentences?

My sister is 17. She's a bright kid who has always put her studies before her social life. She just moved to a new school and wants to meet new people and start dating. She had a little crush on one of my boyfriend's best friends and fellow skateboarder, and added him on Instagram - which I thought was pretty innocent. He liked some of her pictures, she liked some of his. Eventually she gave him her number, but he never texted or called her. It was her first attempt to talk to a guy and she struck out, no big deal. Like I said, she's still a kid and she doesn't have any experience with this sort of thing.

Recently, she started hanging out with another girl at skate parks in an attempt to meet guys. Specifically, she tries to meet guys who are friends with my boyfriend, since he is friends with most of the people who skate there, and introduces herself as "practically his sister".

My sister has become a laughing stock among my boyfriend's best friends. He can't hang out with them without her being brought up. They constantly make fun of her, they ask him disgusting and inappropriate questions about her (for example, would she suck their dicks, what her ass and tits looks like, things like that). They call her desperate and annoying and stalkerish for trying to talk to them, but lead her on by friend requesting her on Facebook and following her on Instagram. They like her pictures all the time and tell her that she's 'pretty' and 'cool' so she's convinced that they actually like her (and why would she think otherwise?).

My boyfriend has asked them multiple times to stop, and they don't take him seriously. I feel like I should tell my sister about it, but my boyfriend says I shouldn't say anything because she'll get hurt. I don't know what to do. I feel like a terrible sister and that I should be doing something to protect her. I don't want to get between my boyfriend and his friends, but I can't sit idly by and let them make a fool of my sister. What should I do?
<bot>: my inexperienced younger sister tries to talk to my boyfriends friend and ends up being made into a laughingstock, I feel like a failure of a sister, don't know what I should do, please help.