
This si the time that a womb infection is most likely after a sesdon(mated or not) and excessive drinking is one of the classic signs. this is an emergency so she needs to get her to the Vet ASAP.
She should mention she may be pregnant, though if she has a bad infection I would not be expecting a happy outcome on that score.
If breeding from the bitch is very important and it is Pyometra, then it can b e treated with Prostaglandins and the bitch be mated next season, when antibiotics may be needed, as the bitch is more than likely to get Pyometra again, and should be spayed once she has had the litter.