I don't think the big girl meant to make you sad and I don't think she was laughing at you. I think maybe she didn't realise how little you are and she used big words you don't understand. But "affirmation" means letting people know you like them, you love them, letting them know they are OK. That is what you were trying to do for Audrey.
You are being very brave and very kind to help Audrey. Maybe you should all go and get some sleep now - it is late here and you must be tired. Sometimes things seem worse when we are tired. I will be here tomorrow and maybe we can talk then. I have to go and get some sleep too but I will stay online if you don't feel safe and need to talk some more. But I do think going to bed might help.
elsie