Long story short, my girlfriend got me a Nintendo 3DS along with two games for it for xmas and even though I really like it, I had previously bought myself one back in Oct. She didn't know and I guess she thought it would make a great gift. And it was... but like I said, I already have one. She got it at Best Buy and I guess at the time she purchased it, Best Buy was having some kind of sale with it- Anyone who bought a 3DS also got a $30 gift card.

So my question is, if I return the Nintendo 3DS will I have to return the gift card that came with it as well? The gift card was free, as it came with the DS. Also, i opened the system when i got it because I didn't want to tell my girlfriend I already had one as I knew that would kind of ruin Christmas for her. She gets real sentimental and if I would of said, "oh, sorry I already have it" I know she would of gotten upset.

I know I could just easily say something is wrong with the DS and have it returned, my question is whether or not I could actually keep the giftcard. Any help would be helpful, thanks!