Help! My Kitten is very sick!?

Hello. I have a 3 month old kitten and she is refusing to eat. She's very thirsty and weak. She stumbled down 2 flights of stairs and calasped in exhaustion. He heart rate seems to be VERY fast. The only thing she has eatin was a tiny bit of chicken. We tried milk, wet food, and a fomula, but she is still weak, has diarehha and is spitting up. We are going to take her to the vet asap but are worry that she wont make it through the night. Any adivice?!