What is wrong with my dwarf hamster?

She's about 3 months old and her sister died about a week ago, so I changed the cage which was a habitrail ovo suite. I read that it was practically a hamster death trap so I switched from that to a tank which I filled with shredded paper. She has always been very active, but now she is easily scared. I was playing with her today when she heard a loud noise and kept running to me continuously. I put her back in her home and she has been resting. She has never been afraid of me or anything for that matter. I don't know if this is realated to anything but her poop has been a little green latley and a little bigger. I don't really feed her any greens and she drinks ALOT of water. Does anyone know what is going on with her?