Oh no, it sounds like she is only getting worse. If I were you, I'd just show up at the vet clinic as soon as you can and I'm sure they will take her in and get her started on fluids and stuff. The longer she goes without eating or drinking, the harder her recovery is going to be.
Is the clinic open today? If not, the 8:00 in the morning time sounds like the next best thing, unless you know of another vet that is open today.
Once she is in your vet's care, they will be able to take her temp and get her fluids and try different drugs etc.. and you won't have to worry as much if she was at home in your bathroom while you are helping your SIL. You have been trying so hard to help her but she may need some more serious attention that the vet and staff can administer.
Sounds like this is your plan anyway but I think you would be better off just showing up because that way they won't schedule you a time that won't work with your time to meet up with your SIL. It shouldn't be a problem for them to take her in and work on her (exam, tests etc..) when they have an opening later in the day. If she is in really rough shape by then, they'll treat asap!
Please keep us updated. I hope she will take a turn for the better very soon.