My MIL has been living with my partner (her DD) and I for about 18 months.
When she first moved in, we set contributions at £400pm. She was still in the process of selling her property and had ongoing bills, so fair enough. She agreed at the time that her contribution would go up once the sale completed. That happened about 2 months ago.
We reminded her on Friday about the promise to up what she was paying. She’s declared that she “doesn’t agree” that she should, mainly based on my DP’s DD (her granddaughter, early 20s) paying less. We’re not charging my DSD much because she’s trying to save a deposit and she’s not on a massive salary (but does work FT).
My MIL’s £400 goes a long way. We cook for her, change her bed linen, provide support on admin tasks, take her to her (many) medical appointments, shopping trips when she wants to go out and it covers all her food, electricity, our additional heating costs etc - basically everything.
She has mobility issues and can no longer cook anything more than a microwave meal (and even that only with some help). She helps load and put the laundry on and she will help with loading and unloading the dishwasher on occasion. She’ll occasionally wipe down the kitchen tops. I don’t begrudge what she does and doesn’t do, just adding it for context.
Her regular income from various pensions is good - she’s not scraping around for money, particularly now that 99% of her monthly outgoings stopped with the sale of her property.
AIBU for asking for an increase in her payment to £600 pm?