Lethargic and in corner

So last night my Chin of 2 years Luna was fine and active looking for attention as always, today she came out, took her bath, drank a little water and since then has been laying the corner and not active at all. She's yet to be sick since getting her and now I'm very worried since I know things can get very serious very fast, I called the specialist and made an appointment but it's not until tomorrow morning. I'm very nervous that she wont make it because I dont know what it could be out of all the possibilities. I'm trying to just give her space for now but I really dont want to lose her over night. She gets unlimited hay and also is given a little bowl size of pellets and he treats are crunchy rainbow colored pretzels meant for Chins. She gets plenty of run around time this seems to have come out of the blue. Any information is greatly appreciated