Some gliders just prefer a bowl. You can take the bowl out, so she has no choice to drink from the bottle. Since she knows where and how to use it I doubt she will refuse to drink from it when she needs to. You can put a little bit of 100% apple or cranberry juice in the water to persuade her to drink it and slowly lower the amount each night. Some people put a little bit of yogurt or honey on the ball, so they want to drink from it. Once she gets in a habit of drinking from it, remove the honey.
By the way, people hardly ever see their Gliders drinking water, because they drink such a small amount. Gliders get most of their fluids from fruits, so they don't drink water that often. Maybe you just don't see her drinking when she really is. To make sure she isn't dehydrated, pinch the fur on the back of her neck. If her fur stays up like a tent, she is dehydrated.