I don't know your age or how close you are to your Mum but honestly everything said previously is just fact and to be very blunt to have a hamster as a class pet is just cruel can you sit with your Mum show her all of the comments and also do research together so she understands and comes to the right conclusion as you already seem to have done. BTW someone on here has lots of knowledge regarding Guinea pigs they can be kept in pairs or group are sociable and are awake during the daytime look up more advice on their suitability it could be a way for your Mum to turn things around good luck and very best wishes with your endeavours.