I know next to nothing about "fit woman" Felt bikes. Recently, I purchased a 2011 Felt TK2 Track bike. I really liked the look of the 2011 versus the 2010 and I could have had either and saved $100 by buying the 2010.

i looked at the ZW4 and it looked hot. The ZW6 "not so hot". Must be the colors. Also, the ZW4 costs twice as much as the ZW6 or about $1600. That is a lot of money. And the ZW4's fork looks steeper to me in the pics. IMO, the ZW4 is a very nice racing geometry bike with higher end components including the carbon seat tube and carbon saddle - not cheap stuff.

I think your intuition to think about this is well founded. Either bike will work in practice except we live in a world of what makes us feel good. Women have great intuition and you should think about this and get what you want.

My wife is a great cyclist and she sees bikes similar to handbags and shoes. It is something that makes her look good as well as performs well. Men may or may not get that and some women do not care. If the 6 bothers you, you should not have to endure it. It is why we have lots of options. Good luck.

Edit: I got the part about swapping the better components to the 6. The look and the ride of the bike will not be affected that much by Ultegra v XXX. The wheels are different. Nicer wheels are better looking and theoretically faster.