I don’t know if you’re accepting any new nieces or nephews, but I’m always on the lookout for new uncles that like to support bass interests…
Yes! A short scale bass would be ideal.
There are lots of cool options out there.
The only thing that mattered to me on my first bass was what it looked like. Granted, I had to buy it myself, so I was part of the process.
Depending on how picky the kid is, it may not matter how good/bad the bass is if they don’t take to the look.
If it’s just about quality and comfort, I really love the Fender Squire Mustang basses - the classic vibe 60’s ones.
There are also plenty of threads here about short scale basses to check out if you need some other ideas of brands / quality / etc:
or this one:
As for the strings:
I would say normal strings, but I don’t know why.
Know your audience, I guess. If she’s into colored strings, maybe?
When I was 10 I wanted something that looked like my favorite players.
Best of luck.