A second kitten would be a GRAND idea.

But in the mean time, she is probably overwhelmed by a new home and lonely for her siblings. If she is not already confined to one room, please do so. Many reasons for this. Mostly so she is close to everything. Nothing like a very large house (and to a small kitten, 4 rooms could seem very large) to get lost in. And also so you know where she is and you can sit with her. You needn't pull her out of a hiding spot right away. pet her right where she is, if you can. Talk to her, do quiet things in the room with her. Stay low, on the floor, you will seem less intimidating.
Bribe her. Treats, interactive toys (strings, fishing rod toys, etc), canned cat food.

And give her time. She'll be OK

Now back to getting that 2nd kitten.....