If someone says they want to help.... here's what you say!
I've been my mom's caretaker for about 4 years. I've heard the "i wish I could help!", "How can I help?" "What do you need?" A million times, from everyone from siblings to church members. I quit saying nothing! My answer is now, "If you wanna invite her for an evening, that would be great! Ill give you a quick list of dos and don'ts, but for a couple hours, you'll be fine." If they're really hesitant, a couple hours after she goes to bed, you can literally be a baby monitor, I'll be half an hour away if you need me.
Call their bluff. At best you get a few hours, at worst they have to admit they're full of shit!
Either way I gain something.
I've actually got a few Saturday nights to myself, one was literally sleeping in my car.