Hello and welcome
I'm not sure which country you're in, but tubes aren't really necessary for hamsters and they do have a tendency to just nest in them and pee in them. They do better with a short run like a tunnel at floor level in the cage like a kitchen roll inner tube etc.
The main thing though is your hamster is in really quite a small cage and I'm also wondering if the bar spacing is maybe a little wide and they may escape. So at the moment, at least the tube is somewhere else to go
Providing it's secure and she can't escape at any connections.
I know it can be hard to find good cages in some countries, but in that case, the best option then is something like a large plastic tote bin and you then mesh the lid so it has a secure top with plenty of ventilation.
If she is hiding away in the tube it's probably just because it's new and she's decided to nest in there. Have you got a name for her yet?
Does she use her wheel at all? That looks like it might be a little bit small as well. She may just be coming out at night and using her wheel when you don't see her. If things were going better before, then maybe remove the tube again (if that's possible and you haven't cut a hole in the cage for it?) and see how she goes, but maybe you could let us know what the bar spacing measures on the cage? ie the gap between the bars. It shouldn't be more than 1cm or she might try to squeeze through at some point.