I wasn't really going out of my way to get a Spider-Girl; I was actually trying to get the rest of the pieces for the Abomination Build-a-Figure I had parts of. A seller on eBay had a couple of the parts I needed. He also had a special where if you bought 2 things you got a third free. Since I was already buying 2 things, I might as well get the third thing for free, right? I looked through his inventory and saw a loose Spider-Girl Marvel Legends figure and so for the hell of it got that for my 3rd item. She might not technically have been the free one but whatever.
I've seen her in a few comics, both the Ultimate Marvel universe and the regular one. She's a different character than Jessica Drew, aka Spider-Woman, though obviously they both have spider powers. Spider-Girl has what looks like the 80s symbiote suit Spider-Man wore, only I don't think hers is a symbiont.
I was Googling for a comic book picture and found someone's much more comprehensive review of the figure if you want to know more about it.
Other than a Build-a-Figure piece, I'm not sure what she was supposed to come with. Just the figure is good enough for me.