She's still young and settling in so I'd suggest giving her time
Personally I wouldn't feel there's an immediate need to upgrade her cage right away; get to know her preferences and allow her to settle in; this will also give you time to look at different cages and see what may suit. Different cages suit different hamsters
I like bin cages or tank cages for my Chinese, with diabetics in narrow barred cages for better ventilation. I don't like the modular cages as they are hard to access and clean.
My Chinese do like to snuggle down under nesting material or substrate in a cosy spot to sleep. They like having a nest box, even if it's just a cardboard box, so they feel secure to sleep.
I like at least 4 inches of substrate in the cage - most of my Chinese will burrow but some prefer to climb! Having more substrate means also that it can be longer between full clean outs (with just spot/partial cleaning in between) which I find hammies prefer so their scent isn't removed entirely as often.
Are you feeding every day? To reduce selective feeding, you can feed a good amount less often. I'm not familiar with the foods you're feeding so not sure whether there would be an alternative.
Congratulations on Chinesey ownership