AITA for telling my friend his girlfriend sucks?

Had to reupload this.

So, around September my friend (We'll call him John) started dating a girl (Who we'll call Anna.) So, as some background, Anna was known for dating a bunch of boys around the school and getting really expensive items out of them, now of course everyone found this really odd, but most people disregarded it. Now this is where John comes in, John started getting close to people in Anna's friend group and this led to a friendship between them (as it usually does.) Me, him and another friend who I'll call Oden, were in a group call together playing GTA 5, when John starts talking about how Anna said she liked him, and I start talking about how that dating her was a terrible idea due to her history, yet Oden was saying he should go for it. John ended up listening to Oden and started dating her, immediately the relationship was rocky, with a ton of arguments between them and even a threat of a breakup. But besides that, John insisted he was fine. Then we get to October, me John, Oden, Anna, and some other friends were sitting at a lunch table when all of the sudden Anna starts asking John for multiple really expensive pieces of jewelry (Amythest neckless, bracelets, you name it.) And at first it seemed like John brushed it off, but literally the next day he was talking about buying a THREE HUNDRED DOLLAR NECKLESS, now take note we are all 16 so this is a massive purchase, me and Oden start telling him about how he shouldn't do it as that money was important for him to save up, but eventually he caved in and bought it. But before he gave it to her there was talk she was actually bad mouthing John to her friends, talking about how much she wanted to break up with him AND that she was seeing a different guy behind his back (this ended up being true.) Of course this gets to John, and he gives her the neckless but also breaks up with her. Now we cut to last month, Anna broke it off with the other guy and tried to date one of me and Johns good buddies, but that didn't end up working out for her. During this whole period Anna would turn around when John started to walk in her direction or was even just passing by, ignoring him completely and even trying to start rumors about him (don't know why??) But in February Anna starts talking to John again, even walking in the halls with him, and of course they get back together, and she's been emailing him about how "he's the only one shes ever truly loved" and that kind of thing. But I got genuinely upset at this, because the first break up made him genuinely consider drinking alcohol (thank god he didn't) And of course I didn't want that to happen to him, so I start telling him how he's just being manipulated and she just wants him to buy stuff for her, and that the same things are just going to happen. John didn't like this at all and has been really distant towards me lately, and this is a friendship I really value so I want to know what I can do to repair it.