Cats are weird about drinking water from a bowl. I have a fountain that is a lot of trouble but they really drink the water. Before that, mine would drink from a sink or shower where the water may not be the freshest throughout the day, especially if it's time to clean. If you can restrict her access to alternative water sources, she will drink from the bowl.

Cats that eat wet food do not need as much water as the dry eaters.

It also depends on the cat. Sam drinks way more water than Spunks.

The gum issue will unlikely go away. Address this issue and she will feel better. Try to stay on top of it, since the critters do not let you know something is wrong until it is bad.

Good luck.