Hello and welcome
I'm in a similar situation at the moment with a new baby hamster. And doing similar things. Every 2 or 3 nights I lift the roof of the house and he is happy to walk into a tube with cucumber at the far end, and have some handling time in the bathtub (apart from the night he jumped off the sofa and escaped but that's another topic!). He also doesn't come out until well after I'm asleep.
She is probably still a baby and a bit scared - and they stay hidden until after dark. As the others say, she will gain in confidence in time, but they do all have different personalities and some will always be a bit shy. What can help with Syrians (who often do wake up very late anyway) is to get them into a habit of waking at feeding time. If you put the food and fresh veg out around the same time every night - maybe 6pm or 7pm and make a little bit of cage noise while doing it, they soon get in the habit of expecting food at that time and waking up for it - especially the fresh veg - they love that and can smell it. That can be a time to offer a tube for them to walk into for some out of cage time.
At the moment, mine doesn't even come out for his fresh veg. He waits until lights out! Some nights he'll nip out and sneak it if he thinks there is no one around.
So it's a combination of getting used to you and time as they grow in confidence in their environment.
It's a big adjustment for them - the first time living alone usually, new house, new cage and environment. It can help to have a nightcam (ie babycam or small indoor security camera) because you can watch next day and see what they get up to. It's also good for checking there are no issues in the cage (eg wheel stuck) and that they are drinking ok.
It's just time and patience really, but a little bit of encouragement as well. They get more used to you and handling with out of cage time, but you can't push it too much either.
Do you have a playpen? If they get used to being able to run around more in a playpen - and maybe have a spare wheel and hides and tunnels in it - then they can start looking forward to out of cage time and start wanting to come out.