Help! Finch baby won't drink water!?

When we got a batch of Finch babies two months ago, we were all overjoyed of course! We've never had baby Finches before, so we were also kind of scared because we didn't know what to do. Of course, with every batch comes a runt, and what a runt she is! Although, things aren't so good for our little runt. She can't fly well, and has a deformed foot. We set some perches on her level and a little nest on the ground since she can't fly up to her family, and we also ALWAYS set the food on the ground on a little dish, which is spinich and eggs, every morning. The only problem right now is that she doesn't understand how to drink water. We've set a water dish on the floor, we've set one of those hamster water bottles on the side of the cage, and we've even set a water dish at her level on the side of the cage. She just doesn't understand it. The only way she knows how to get water is by drinking the drops that fall out, and sometimes she likes it when we squirt her with the spray bottle. None of the other finch babies have this problem. What can we do to help her understand? :(