The Dog Days of Charlotte Hayes by Marlane Kennedy

It's not that Charlotte hates dogs. Or that she wants all of them to disappear off the face of the planet. It's just that she doesn't see why everyone loves them so much. So how did she get stuck taking care of a big, drooling Saint Bernard puppy? Rain or shine, hot or cold, poor Beauregard is left chained in the backyard. No one ever plays with him or checks his food and water bowls, and Charlotte can tell he's sad. So she makes sure he has water, gives him belly rubs--blech!--and feeds him every single day. But it's kind of a pain, and she knows Beauregard deserves better. There's a new girl at school who lives in a huge house--plenty of room there for a big dog. Charlotte has an idea. Now all she needs is a plan. Maybe a lot of plans. How do you rescue your own dog?