The norm. They usually go into heat in spring and fall. If you aren't going to breed her, get her fixed, then you won't have problems.
if u have 2 ask this than u should c a vet. yes it can be normal, but lack of energy high water intake can be anything...
My first question would be, why isn't she spay? Healthier fir her.
Second question, any chance she was bred by some make???
What dies the discharge look like now? Color? Any odor?
I would not be taking a female in heat on walks.
Is it hot in your area? Could be the heat so keep her cool.
Do you know how to take a rectal temp with a rectal thermometer? Anything over 103 might be a concern.
Good that she is drinking.
She just may be off her food. If any other symptoms develop like loose stools, vomiting, etc you should get her checked.