MIL takes advantage of kindness

So, I've always been a shy and nice girl and I can't ever seem to say no because later on I feel guilty for saying no well my mother in law completely takes advantage of that and always has me drop everything to help her, one time she literally called me to ask me if I could put her pants in the dryer and I did it yes she can't walk far because of her osteoporosis, but I live miles always and I have two kids and a whole house to tend to it drives me crazy that she always wants me to drop everything to accommodate her needs and then has me do these insignificant menial things which she can do herself I've told my SO to talk to her, but she persists and she always acts entitled to her in laws for things that is not how things work 🙄