Hi, Tina. You are sure not the only one that has a "not me" in your house. Here's how to go about fixing your water spot.
First, remove the glass. Next, apply petroleum Jelly or mayonnaise to the white part and let it sit over night. Sometimes, the oil will replace the water in the finish if the damage is superficial.
If that does not work, put a little denatured alcohol on a soft cloth and wipe it briskly over the damaged area. Begin with very little alcohol on the cloth and keep the cloth moving. Don't rub hard, just fast. Shellac is damaged by alcohol and if appears that the alcohol is removing the finish, stop immediately. The white mark will be gone by then anyhow. If the alcohol does not appear to be removing the finish, you can put a little more alcohol on the cloth but still keep it moving briskly.
If neither of these work, come back and we can go on to the next step. Glass topped tables are famous for allowing water to get under the glass and it is not noticed until the finish is heavily damaged. I hope that this is not the case, but try the first 2 solutions and see how that goes before we move to the next step.