I (15F) am tryna help my friend (14F) with her situation with her bf/ex (13M) to get back at him.

I (15F) am tryna help my friend (14F) with her situation with her bf/ex (13M) to get revenge. So my friends bf, we'll call him noah, has genuinely been a ho from the start. He's always been chasing girls, that's literally all he does, he's asked out multiple girls in the past year (and been rejected). Im not sure if you call this microcheating or cheating though it does really sound like straight up cheating. Noah told his friend Simon (15M) that he thinks my friend, the one who's dating noah (let's call her anna) is chopped and he wants to break up with her and then Simon told me, Noah texts girls he used to like/does still like, flirts with other girls, sends other girls pictures of himself and Anna saying he mogs her to oblivion (but he's really just a lmtn). Noah says things to his girl best friend, nina (13F), like "I used to like you, if only you would've gotten with me I would've made u the happiest girl ever", and to another girl who is his ex (13M) stuff like, let me hold ur waist again ur so sexy, and sends couple videos saying "us when?". We know this because Noah begged Anna to have access to eachothers accounts and since Anna had nothing to hide, she did. But while Anna went through Noahs messages, she found allat. While Anna sends him videos saying shes insecure of her weight and reposts such videos, noah says "oh, you're probably talking about \[girl he likes\], but its okay, its all genetics". Our other friend Lia (15F) wanted to send him a fat ass paragraph saying Anna found out about all of his side chicks, but i dont want to do that. We can't let Anna get walked all over and treated like shit just for her to send a big speech that makes her look like a desperate annoying bitch. What can we do to get back at Noah? Most of our school really likes Noah, (even tho they're all fake) so they'd all be on his side. We can't get Anna to send him tiktoks of hot guys saying "why dont u look like that?" Because Noah and his friends will use that against her every chance they get.