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Each hamster is an individual so you have to try to assess what your ham enjoys & needs rather than going by standards you see online but I do find my Chinese hams have enjoyed plenty of space & tend to be very active busy digging, burrowing & climbing so have had reasonably large but not huge cages, something around the size of the Hamster Heaven is a good size, I prefer barred cages as it allows plenty of easy interaction & as they love to climb you can attach ledges & shelves for them to climb on & it's easy to hang hammocks for them which they love too.
From the food you're feeding I'm guessing you're in the US? If so then you may have difficulties finding a good cage & may want to consider making a bin cage.
They do love small seeds & it's understandable that she won't eat the pellets if she has an alternative, good dwarf hamster foods are hard to find in the US too so if you need to use the oxbow to make up a good diet for her then you will just have to wait until she's eaten them before giving any more seeds, oxbow isn't ideal for them though so I would try to find a mix she enjoys. Some members in the US like to get . Burgess dwarf hamster harvest from Viovet, a UK company that delivers to the US.
The cleaning may have upset her a bit, other than spot cleaning keep cleaning to a minimum, you don't need to do a lot.
They often prefer to burrow down in deep substrate & make a nest rather than use a house but a wooden house or cardboard box (both with no base) will often be used if it's a good size & just sat on deep substrate.