She could be drinking a lot to cool herself, but polydipsia, as it’s called in medical lingo, is generally thought of as an observandum. It should be investigated if it continues, especially if she has an incontinence problem as well – ie if she pees pretty much anyhere and frequently.
Causes range from innocent to grave. It can be about about a UTI or e cuniculi affecting the kidneys, or pretty much any kind of tissue inflammation or mouth pain due to a dental problem (not super-likely in such a young bun).
We have some cooling tips on our info-page. I’d try those first of all. As you know, rabbits are very sensitive to heat, because they originally stem from parts of Europe where it only rarely gets super hot -when it does get very hot, they spend the day underground and don’t come out until sunset.
https://binkybunny.com/infocategory/cooling-tips/
A rabbit should drink about 10O ml of water per kilo body weight and day. A bun that gets fresh vegs should drink significantly less.