I'd only suggest using pee pads if there is a real reason he cannot hold it. Pee pads can teach the dog that it's ok to go in the house. She should have him checked by her vet if he was holding it fine before, but now isn't. If there is no medical reason he can't hold it, then I'd use the crate. Or if she doesn't want to use the crate than is there a reputable pet sitter or dog walker in her area that can come walk him in the middle of the day? Or maybe a trusted neighbor? If she has a securely fenced yard a doggy door may be an option too. Or use a baby gate to keep him confined to 1 room, a bathroom or kitchen with tile flooring.
Maybe she should take up his water while she's away, or only leave a small amount down. Make sure he's eliminated everything before she leaves, and don't keep food down for him.