Hello Lynn and welcome. Congratulations on choosing Chinese hamsters! As souffle has rightly pointed out though, keeping a pair of females together could result in them turning on one another as they mature. Don`t let this worry you right now because as babies/youngsters, they are likely to co-habit okay, but have a spare perspex tank style cage ready (even buying one second hand off ebay) is a good idea incase you need it in an emergency situation. More often than not, people purchase two chinese because they want company for their hamsters. Sometimes it`s because the pet shop/store advise it, when they should know better!
Are you in the UK? If so, you should be able to find a spare cage like a Savic Rody or a Ferplast Duna to have on hand just incase. If they are already in a bigger tank, giving them two of everything would prevent squabbling over things. Two wheels, two food dishes, two water bottles etc....
The Zoozone 1 perspex tank is a really nice cage for one or two dwarf or chinese hamsters. Chinese hamsters can be prone to diabetes, so should not be fed sugars/glucose/honey/syrup or molassed treats or foods. Picking out the yellow corn and flaked maize from your mix would be a good step as corn turns to glucose (natually) and is probably one of the additions in a hamster mix that can be replaced by things like:
Porridge oats (dry)
Budgie seed/canary seed
Buckwheat (dry)
Hemp seed
Dry mealworms (as hand fed treats)
It sounds as though, from your description of both females, that one is quite feisty and the other more laid back, so you may have a mis-matched pair (one dominant, one subordinate) which could mean that the subordinate will stay that way and `know her place` in the ranks. But it could also mean that she might end up being bullied, so do make sure they are kept in a room where you are 24/7 to watch for any signs of one chasing or trying to bite the other. If you see this, seperate them right away. I have a female who lived with another female and she was attacked and had to be split away. This is how I came to have my first chinese!
They really are brilliant, sweet natured little creatures and I`m sure you and your daughter will love having them.