Update:
*sighs* Well, I just dropped her off at the vet's. She's having surgery today. The techs said there's a 99.9% chance she's going to have to stay the night there too (which I'm sort of happy about because then I can pick her up myself and talk to the vet tomorrow, instead of having my dad pick her up again). They showed me her x-rays, and wow... my poor baby He bladder is FILLED with stones.. It looked so bad. I can't believe my Megan has something like that. She's always so happy.

Please send her good thoughts for her surgery. I hope everything goes well. I'm so worried about her..