Wow, that translates to at least 384 ounces. The average amount is 1 fluid ounce per pound of body weight per day. Of course, things like temperature and exertion levels affect that, but that much (3+ gallons!) seems excessive.This article discusses things that can affect their water intake. Dog Always Thirsty? How Much Water Is Too Much? It would be a good idea to have her checked by a vet as soon as possible, to make sure that she's not showing any other signs of possible problems.
My German Shepherd has always drank more than any other dog I've ever owned, and even she only goes through a couple of quarts a day.
I think that much water in that time frame would lead to water toxicity in a human, which can be fatal. When you say "just adopted" do you mean you just brought her home at 9 a.m., and she's been drinking ever since? Are you sure of your measure? I would allow any more water today/tonight, and at least talk to a vet over the phone ASAP. Getting her to a vet would be better.