You know how you said don't recommend stuff you obviously know about? Like Transformers?
This is something I can honestly suggest in a non-nerdy way.
http://tfwiki.net/wiki/Activators
They're spring loaded, pretty small and simple to convert back into vehicles. It's the only Transformer I can recommend that happens to be eight kinds of kid friendly AND dirt cheap, apart from the Deluxe Animated figures, but I doubt she'd care for those.
Obviously I understand if you don't care either way, but I figured I'd throw it out there.
Otherwise, if she likes random monster/alien crap, pick up some Ben 10 Toys. I don't actually know much about them, but the designs are neat.
There's also some generic robot/monster things in the Iron Man: Armored Adventures toyline, also pretty cheap. Same with any residual crap from the new Astro Boy movie, neat designs etc...