Is my mother in law gonna hate me???😭

I’m a 26F and my boyfriend is 30M. We’ve been together a little over two years.
So here’s the situation. His mom lives in another state and came to visit over Easter weekend. While she was here, she basically volunteered herself into our future living situation. At first, she made it sound like we’d all just buy land together and have separate houses, which honestly seemed a lot more reasonable.

Now the plan has completely changed. She’s talking about all of us buying one house together and then eventually building another house on the property later. Realistically, we don’t have the money to pay a mortgage and build another house, and even if we did, I’m just not comfortable living with my boyfriend’s mom.

For context, my boyfriend works out of town about 50% of the time. If we all lived together, it would mostly just be her and me at the house. That feels really awkward to me. Also, he and his mom aren't even super close. They actually went several years without talking before reconnecting.

We talked about it, and my boyfriend agreed that we’re not doing the shared house. The problem is... he still hasn’t told her. She keeps calling him, and every time he says he “doesn’t want to break her heart today,” so he avoids the conversation. I feel guilty watching it get dragged out, but it’s not my place to call his mom and tell her no.— everytime I try to bring it up he just says he’s going to handle it when the time is right.

What I’m really anxious about is how she’s going to see me once she finds out. My boyfriend says he’s going to tell her it was a decision we made together, but I’m worried that in the moment he’ll end up saying something like, “My girlfriend isn’t comfortable living with you,” and then I become the bad guy.
— I mean I know he wouldn’t go into the conversation planning to blame it on me, but what if under pressure he caves.

The truth is, I actually like her. I don’t have a problem with her as a person. I just don’t want to live with my boyfriend’s mom. I already have enough stress in my life, and I feel like that would add a whole new layer of it.

She still plans on moving to our state either way, so now I’m worried everything is going to be awkward. At this point it feels like we’re already in too deep, and no matter how this conversation goes, it’s going to be uncomfortable. I’ve been worrying myself sick over it.

Am I overthinking this? And how would you handle it if you were in my shoes?