Thanks for the answers to my questions and the additional information.
Poor thing, she sounds quite anxious, doesn't she....which isn't that uncommon for some kittens this age (or any age, actually).
To answer your specific question about her not urinating or defecating in 10 hours, I wouldn't worry too much about this. She's far too stressed at this point to be worrying about such things. Some cats will only defecate or urinate once a day anyway although most will go more often than this.
An enlarged abdomen is commonly seen when internal parasites such as roundworms are present which also aren't that rare in young kittens.
I recommend that kittens be wormed every two weeks for three doses with Pyrantal Paomate which can be purchased at most all pet or grain stores (at least here in the States). You can also buy it online without a prescription. It goes by different names such as Strongid or Nemex or Evict but the active ingredient is the same drug. It's a very safe and yet very effective wormer so even if she doesn't have round worms, it's not going to harm her.
I've seen a few kittens this age who become a little constipated and develop an enlarged abdomen; however, she wouldn't become constipated in just 10 hours. If she was producing stool at the home from where you got her, then this isn't likely to be her problem.
Until she's had a chance to settle in, I might consider putting her in a small room (such as bathroom or laundry room) where you can shut the door with her litter/food and water. When she's alone and feels safe, she'll most likely use the box.
By the way, if you're feeding her canned food (as opposed to dry), she's not likely to drink as much water since the first ingredient in moist food is water....just in case you were thinking she wasn't drinking as much as she should.
I hope this helps. Deb