Like others have suggested - take it out of the box and try it.
It will probably seem very "puny" next to your new Bernina, BUT
If the machine has a decent straight stitch and zigzag stitch and the tension behaves itself, she can make many things.
Sometimes, simpler really is easier to learn on and operate.
As far as the opened box goes, just tell your niece that you wanted to make sure that it worked properly before you were comfortable giving it to her.
From your comments, wonder what MIL and SIL were planning to give her for the other sewing supplies?