Smatchet.
Mandatory bladeforums answer. Works every time.
Now, on a serious note, great suggestions everyone. My opinion as follows: If she works in a big box store, she is probably given box cutters / utility knvies for thrassing arround. At least she should. Using a nice knife for opening boxes in a daily basis is going to ruin the edge and the knife in short order, no matter the steel. Then it will not cut as well and unless she learns how to sharpen, she will go back to the box cutters with disposable blades. That if it doesn't get lost/borrowed-never-to-be-seen-again first.
That's why I would decide against getting her a knife for work duty. At least for now.
If she likes knives... Which one of your knives is the one you noticed her liking the most? That could give you some ideas about what she preffers. Also, how long are her LONG nails? I guess not much if she does handwork at the big box store but never hurts to ask. I don't picture anyone with (pardon the comparison) with porn actress long nails opening anything with holes in the blade (spyderco). Even thumb studs could be hard to manipulate. I think a flipper could come handy.
And for the lack of pockets to carry the knife... Well, I she wears yoga pants and they are tight (and if she is 18, they WILL be thight), she could carry inside the waist band. Just make sure the handle texture is not Emerson-rough or Cold Steel-rough... Weight is an issue as well, so try to stay light.
Mikel