AIIW for wanting to end an 11-year friendship because my best friend took my ex's side?

Throwaway because some people involved know my Reddit account.

I'm 30F, and my best friend is 29F. We've been best friends for 11 years. We've been through so much together, and I genuinely considered her one of the people who would always be in my life.

My ex-boyfriend and I recently went through a really difficult breakup. We were together in a long-distance relationship, and one of the biggest issues was that we ultimately wanted completely different relationship dynamics.

When we first got together, he told me he was okay with being monogamous. I trusted him and entered the relationship with that understanding.

Less than six months into the relationship, however, he changed his mind. He told me that he wanted a triad relationship and that he felt more fulfilled by that kind of relationship.

I tried to understand his perspective even though it wasn't what I wanted. We had a lot of difficult conversations and disagreements about it, but eventually it became clear that we wanted fundamentally different things.

*We broke up.*

About a month after the breakup, my ex and I were still communicating occasionally, and that's when the issue with the gifts happened.

He brought up an old MacBook of mine. It's an older model that he apparently wanted for his "vintage" collection. He asked me whether I wanted it back.

I told him no. I had already given it to him, so as far as I was concerned, it was his.

Then, completely out of nowhere, he brought up the monetary gifts he had given me while we were together.

He said he wanted them back.

His reasoning was:

***"Only good partners deserve that kind of money."***

And this honestly pissed me off.

Not because I was desperate to keep the money, but because I couldn't understand the principle behind it.

They were gifts.

I never asked him for those things. I never pressured him into buying them. I never demanded expensive presents. He willingly gave them to me while we were together.

And now, a month after we had already broken up, he was essentially saying that I only deserved those gifts if he considered me a "good partner."

I was angry and needed to vent, so I called my best friend.

I told her the whole story and said something like:

***"IT WAS A GIFT. Where are his morals if he wants his gifts back now? I didn't ask him for any of this. He willingly gave them to me and now wants them back because we're no longer together?"***

I expected my best friend to at least understand why I was upset.

Instead, she said:

***"Girl, I love you, and you mean the world to me, but I believe he's right."***

I was honestly stunned.

Then she added:

***"I did that to all of my exes, remember?"***

And that's the part that really messed with my head.

My best friend's previous relationships ended badly. Her exes cheated on her, and she responded by secretly cheating on them as revenge without them knowing.

I never held that against her. She's my best friend, and I understood that she was hurt and dealt with those situations in her own way.

But when she said that, I couldn't help thinking:

Does she actually see me as being in the same category as her exes?

Because I didn't cheat on my ex.

I didn't betray him.

I didn't manipulate him into buying me things.

I wasn't demanding gifts from him.

I genuinely tried to be a good partner. I was understanding and considerate, even during times when I felt he was being unreasonable.

Our relationship ended because we wanted different things. That's it.

So hearing my best friend of 11 years basically agree with him and imply that he was justified in taking back gifts because I wasn't a "good partner" really hurt me.

And now I'm questioning our entire friendship.

Maybe I'm taking this too personally. Maybe friends can disagree about something this significant without it meaning they don't value you.

But at the same time, I can't shake the feeling that this wasn't just a disagreement about whether gifts should be returned.

It was the fact that my best friend heard my side of the story and immediately sided with my ex, a month after our relationship had already ended.

I don't expect my best friend to blindly agree with everything I say. I actually value honesty and would rather have a friend tell me when I'm wrong.

But there's a difference between saying, "I understand why he feels that way, but I don't agree with him," and saying, "I believe he's right."

Especially when the reasoning behind it is that I apparently wasn't a "good partner."

So now I'm wondering:

Am I overreacting if I end an 11-year friendship over this?

Or should I talk to her first and try to understand why she feels this way before making such a drastic decision?

I don't know if I'm ending a friendship over a disagreement about gifts, or if this situation simply revealed something about how my best friend actually views me.

And honestly, after 11 years, that realization hurts more than anything my ex said.