My SO's mother is the same way. Nothing he does will make her happy and she complains about everything. Some people like to complain; it is like a hobby to them--that's my SO's mother. We just ignore her. We don't go out of our way to do special things for her, since they aren't appreciated. We only offer to do things for her that aren't going to be a burden or a problem for us. When she complains, we just don't respond. You can't win arguments with a professional complainer so it's best to just not engage.
It is incredibly frustrating and my SO does still sometimes get sucked into arguments with her. The funny thing is that she wants me to gang up with her against him (which just shows how crazy she is that she even thinks I would do this); since she's trying to make me her buddy, I can do no wrong. She'll complain (in an annoying back-handed way because she knows her complaints are inappropriate) that he doesn't spend enough money on her Christmas presents but go out of her way to say that my presents were perfect, even though I will have spent way less on her. This year I think all of our gifts will be from the both of us--I wonder what she'll do with that.
You can't control other people, all you can control is your own response. Since your MIL doesn't appreciate favors you do for her, either don't do them or do them without expecting any thanks. Isn't there a saying that insanity is doing the same thing over and over again but expecting a different result. Your MIL isn't going to change, no matter how much you go out of your way for her.
Also, Glory is right, you don't have to spend time at his place. For the first three years that we were dating, my SO lived with his mother. As a consequence, we spent all our time together at my place. And I mean ALL--literally, I did not go to his house once that entire time, except for when she was out of town. People are constantly pressuring us about getting married, even back then, and because I always ended up cooking when he was at my place, I used to joke that he owed me three years of dinners before we could get married (unfortunately, after 11 years, this joke doesn't work anymore

). But spending our time at my place worked really well in that 1) we hardly ever saw her and 2) she eventually figured out that if she wanted us around, she would need to behave better.