AITAH for siding with my other bestfriend instead of siding with my friend?

So my friend, let's call her Prudence and my other best friend let's call her Sunny. Me and sunny are best friends since second grade, yada yada. Prudence was just there but never close enough to us.

Once me and sunny fought and I fell off with her. Prudence got close to Sunny because it was the right opportunity. Prudence is really insecure and gaslighting. She talked shit about Sunny to her other friend and vice versa too when Sunny and that friend fought.

Sunny dated this guy and later broke up with him. Prudence was always jealous of their relationship and somehow managed to date the said guy afterwards.

Fast forward, a year later Sunny started dating this tall guy. GUESS WHAT. Prudence befriended this guy and started talking to him too.

SO whenever Sunny and tall guy fought, Prudence "acted" as a mediator. Well mostly she would go tell tall guy about what Sunny told about him. And bitched about Sunny too. Mind you, prudence was still dating the said guy. She never admitted it but I think, prudence had the hots for tall guy since then.

A year later, Sunny and tall guy mutually broke up. Three months later, Prudence broke up with that her boyfriend. Quoting some bullshit and alleged that he kissed her without her consent though I heard something else from a mutual friend.

But they broke up mutually right? But prudence went around saying it wasnt mutual and basically that Sunny broke up with him due to her commitment issues. :/

Then 2025 came around. Now I didnt know about any of this until an incident happened.

Around October 2025, Prudence came upto me saying she needed help. I as a caring friend asked her what it was and she told she needed my help to talk to the tall guy in real life (we're all in the same class)

Now i genuinely believed she wanted to be friends with tall guy cuz they "fell out" after sunny's breakup. And i told her, if you wanna be friends with him, go for it. Dont worry about sunny and stuff"

I told Sunny about this and she told me prudence can be friends with tall guy for all she wants but...Sunny told me she had a feeling prudence was gonna date tall guy.

AND SHE DID. PRUDENCE STARTED DATING SUNNY'S EX BOYFRIEND, ONCE AGAIN.

But prudence came to me the day before and told me that tall guy confessed to her. And that she likes him back. I told her to drop the issue and not continue anything and she told she will but...three days later I found out she dated him and then broke up. In a span of three days, yes.

Then she blamed it all on me for not being there for her and being a good friend and siding with Sunny. She quoted "I was confused very much and I couldnt move on from him. And you weren't there for me."

But last month, february 2026, I learnt that Prudence and Tall guy got back together in november 2025 and are still dating in secret. And she lied to my face.

So am I the asshole for siding with sunny? And please, how do I confront this shit? My self respect went down the drain after I argued with Prudence but i let it slide.