Some Syrians are just small, in fact I believe they are now artificially large due to selective breeding practices. Originally hamsters were much smaller than they are today, and some colours even seem to have a propensity to be larger than others, someone with a great knowledge of genetics may know the reason why...
but it is more than likely just down to selective breeding again. Successive inbreeding does tend to produce smaller Syrians, which is something I actively discourage
Some of my "show" hamsters are huge
as big as a small guinea pig, and I have others, especially those obtained from petshops, rescues etc. that are almost half their size and look like they are permanently 10 weeks old
As long as she is happy and healthy then I would not worry - but if it bugs you a lot then remove the igloo and give her some large cardboard boxes, toilet roll tubes etc to hide in as she is obviously a private hamster
I know a few people do prefer not to use these plastic type houses due to condensation and a hamster will happily sleep in just a pile of shredded toilet tissue. We should respect our little one's privacy though and if they prefer to hide away in somewhere they obviously like, for whatever reason (maybe safety or security - who knows - some are less social than others), then it is fairest to provide them some hidey-holes still.
Ultimately it all comes down to breeding and socialisation. Have you considered light levels in your room
Maybe she likes the dark for her daytime slumber
These wierd habits are all part of the fun of hamster ownership, or
ownedship they like to make us worry