AITA for pointing out to my ex that this is what she wanted?

My ex and I divorced 8 years ago, amicably. She is the one who proposed we didn’t make the kids switch back and forth for the time being. We’d each spend 2 weeks at the house and switch on and off. She said we’d do this until one of us moved on and got remarried, as obviously that wouldn’t be a realistic set up. I agreed and we put it in writing, including that this custody arrangement would only last until one of us got married. We also split rent on an apartment that the other lives in during their “off time”. All bills have been split evenly between both. Per the agreement, when this ended, we’d sell the house and split the profits, as it’s in both our names. Our kids were 6 and 8 when this began, they’re now 13 and 15.

I have been with my now fiancé for 3 years. We started living together at her place 2 years ago. My ex also started living with her boyfriend so we gave up the apartment, and would still switch off living in the house during our custody time. While our partners didn’t live at the “main house” full time, they have gotten to know our kids and everyone gets along. The kids love my fiancé and are excited for the wedding. My ex was happy for us until I spoke to her about putting the house on the market.

Suddenly, she got weirded out and said she didn’t want to change the arrangement. It was easier for her and it’s nice to “have a break from her boyfriend every 2 weeks”. I said I get that, but my fiancé and I are getting a new place that’s both of ours. The kids are okay with this, and are fine with having to switch houses at this point. I offered to my ex that she can buy me out, but she can’t afford to do that. She kept saying this isn’t fair and she didn’t “expect I’d ever move on”. I asked what if she married her boyfriend. She said she has no plans of remarrying and thought I wouldn’t want to either. I just said “well, I am”.

We’ve started the process of selling the house and she keeps trying to get the kids against the idea, but the kids honestly don’t care. They’ve loved getting to house hunt with me and fiancé. My eldest wants to help fiance decorate as they’re close. The kids are also excited to spend more time with ex’s boyfriend as they’ll be living with him and their mom. He’s a very nice guy and they like him.

Recently, we got an offer on the house and my ex was very emotional, which I understood. This was a home we purchased together and raised our children in. I’m emotional to let it go as well. But when we were discussing it, she told me this is all my fault that she had to sell her children’s childhood home. I told her that she’s the one who came up with this idea 7 years ago, and she’s the one who put in the clause that we’d get rid of the house when one of us remarried. It’s not my fault that she had some unspoken, unrealistic expectation. This set her off even more and she started sobbing, telling me I’m a jerk for “throwing this back in her face”.

So…am I the asshole for pointing this out? We’ve amicably co-parented for 7 years and I’d hate to see that end over something like this.