I am looking for a good (and semi-cheap) harness for my girlfriend. Any suggestions?

I don't think it's that cheap but the Metolius Safetec harness is fabulous... well, it's great for many reasons but it has a long rise (which means the distance from waist to crotch is longer than usual) which I find to be much nicer for my body type... don't know your body type but I know that a lot of women tend to be longer in there.

My daughter recently got a Black Diamond Primrose AL. My impression is that it's a very good, all-round harness with excellent quality/price ratio. You may also want to check out the Women's Wild Country Vision, which is another good quality, reasonably priced harness. You probably already know that it's better to try a few on to find the best fit.