Couldn't really hurt to wait around till black friday/cyber monday. The prices of kindles are pretty stable so don't expect too much. The kindle i have is I think the 2nd or 3rd one, and it works perfectly for me. As for the ads, I'd pay the extra to get rid of them, but I wouldn't really know, seeing as mine doesn't come with them. One thing that I have seen about the ads is that they are only when you lock the kindle, and in the shop or when looking through your list of books, not actually when you are reading. Also, some of the ads are apparently special offers, and although i'm not really sure what that means, maybe some people would be interested in special offers from amazon?
Something else to factor in that you might be forgetting is if you want the kindle to have built in 3g. The 3g might be helpful if you go on a road trip or something and your girlfriend finished the book she was reading and has nothing else to read. Honestly, it's not too useful, but I have used it in a pinch for other browser related things.
Lastly, what model do you think she would like? As of right now there is a Kindle, Kindle touch, Kindle with keyboard, and soon to be a kindle fire(think tabletish)
Hope all that helped!
