Hi sashacarly, Kitten poo is very small compared to an older cat poo, is she litter trained from the place you got her from, just keep an eye on her and if need be put her on the litter tray if you think that she's not using it and going somewhere else to do her business.
Some times kittens get stressed when they are taken from their mother and siblings, do you have another cat for its companion to help it settle in better. I wish you lots of happy years together. X X X :-)