Why does my wife feel this way about me?

I feel like I do a lot for my wife and her mother. I do things around the house and around my mother-in-law's house. I also do financial things like take care of her mom's tax issues when the state mistakenly billed her twice and then added penalties. Her mother doesn't like me much and will do things like intentionally leave my place (only) unset at dinner and so on. I said something the other day and my wife said that she's "tired of being around immature people." She meant both of us, me and her mother. I feel this is unfair since I have not done anything to her mother but help her. Is this fair? Why would she say this?