I just want to know if it works for them. My gf is using a 1.6Ghz celeron with 512mb of RAM and she hates it. It is a very personal thing. I think 2GB will be fine. Just wanted to check.
You can ask 10 people and they can all tell you it works for them. Then you buy the 2GB Air and if it didn't work for your GF then the idea of asking those 10 people wasn't the best idea. Now based on the fact your GF is coming from a PC with very low specs she'll probably do very well with 2GB ram in the Air.
But honestly, a better question would be, just an example; (My GF needs to run Photoshop CS5 and she won't be using the computer for much of anything else, she doesn't do much web surfing, nor does she do emails very much, would 2GB be enough for Photoshop?).
That type of question would give you a more accurate return on whether or not the 2GB would be good enough. But if it's all about money for you then you know what to do.