Something's wrong with my dog but my grandmother won't listen?

I am 18 and my mom and I live with my grandparents. For about a week our doug has had a dry/warm nose, she's been extremely thirsty and doesn't eat as much as usual. I have told my grandmother to have her checked because there is something wrong but she won't listen to me, she says the dog is fine. With the dog food recall thing going on, this is really worrying me but no matter what i do or say my grandparents wont take her to the vet. What should I do?