I don't want to voluntarily offer to help do my grandmother's yard work.
Why don't you want to help with your grandmother's yard work?
She makes my life much harder.
I know that you don't get along well with your grandma, but not helping her with her yard work when she needs you is not respectful of her age. Go to your grandma's house and offer to work in her yard.
Why does she need all that help now, her yard looks fine.
Helping family is very important, especially older family. You'll want some help too when you get older.