Bitch won't stop complaining about distance.

I'm new posting here so some quick background: SO and I have been dating for 3 years, engaged for 4 months, and the wedding isn't until 2019. We are currently living at my dad's to try and save money for an apartment in a city nearby and so we can help my dad remodel is house as a trade-off for living rent free.

My FMIL has literally never run out of things to complain about, which I know most of you, if not all, can relate to. My SO's family comes from a very small town where the only thing to do is peer out the window and bitch and gossip about every little thing going on. This weekend, we drive 3 hours to see his family for a birthday celebration. The first thing FMIL has to mention every time we go to see them is how she never gets to see her boy because he lives so far away and how he "must be too busy with other things" (pointed look at me, like WTF bitch he's not a momma's boy). In the 3 years we've been together, FMIL and FSFIL have actually made the effort to drive the three hours 3 TIMES and one of the times, it was only to get meat from a butcher in our town. Meanwhile, SO and I are expected and guilt-tripped to come out AT LEAST every three months or so, regardless of the fact that we were both in school and had full time jobs. They are both free on weekends but don't believe that it's up to them to make any effort to come see us. My SO actually had to give FMIL an ultimatum to even get her to come out and see him propose to me. Needless to say, I'm pretty sick of her constant nagging when she's constantly a fucking hypocrite and she puts SO and me in a sour mood just by mentioning it.

If that wasn't enough, she would also get pissy because every other weekend my parents (who are divorced and still get along) came up together to see me and take me and SO to lunch or dinner. I wouldn't ask them to, but they only lived 1.5 hours away and would do the same for my brother when he was in college 2 hours away. So she figured that of course my parents were just trying to make her look bad, regardless of them having never met her, and would constantly make backhanded comments on how my parents must just be so much better than she is, and how SO must like being with them more than his own mother, who, honestly, hardly even acted like a mother when he was growing up.

Recently, she's become even more pissy because my SO and I moved in with my dad, as I mentioned before. She thinks that we should have considered moving in with her and FSFIL even though their house is barely big enough for them and they live in buttfuck nowhere with no job opportunities. On top of that, it's STILL 3 hours away from them and they have made no attempt to come see us and they didn't even offer to help us move. But of course, it's my fault because SO is apparently showing favoritism and he hates his mother because of me (BUT it can't be because she can't even remember what he's allergic to and cooks things he can't eat every time we're there). We have explained to her exactly why we moved in with my dad, but she's not hearing any of it, telling everyone that she can that she can't see her son because he has to live with his fiance, soooo far away. She doesn't understand that my SO has been trying to distance himself from her for years and that he really doesn't like being around some people in his family for long, including his mother. She has only started acting like a "mom" in the past couple years, after we started dating. Otherwise, she wanted to be a "cool" mom when he was growing up and hardly ever acted as a source of authority. He is 23 now and fucking sick of his mom acting like she was a saint for all those years and that she gets to tell him what he can and can't do now that he's an adult.

I realize that this is probably a common complaint that most of you have had with your own MIL's and I am one more needy phone call away from telling her to just shut the fuck up. I want to try to talk openly with her because she's gonna be family (shudder) but I just want to know if there is any way to say STFU in a way that won't make her even worse, because she's already tried to get ahold of our wedding plans. I'm a novice when it comes to MIL's, please help.