The B-street would be fine for an all-mountain deck. The BTX is great, it floats well in powder, holds an edge like no other. It's soft, but it has some snap, so it isn't a total noodle.
I only prefer the Pandora because of the added dampening. I don't think the graphics are that bad - women can be so stupid sometimes. Get her some freaking stickers. Her bindings will cover half the zebra graphic anyway.
The Ollie Pop is very similar to the B-street, probably just a tad stiffer. That's actually an excellent choice for your girlfriend.
The B-nice is a good board for beginners and progressing riders, but the shortest size is a 146 I think. It's really not too long for her, but it sounds like that's longer than she's comfortable with.