Because she had the mistaken assumption that the store wouldn't be selling a laptop that was useless, so obviously the only thing of significance that should be different is its cosmetic appearance. She probably also bought a car based on its shape and color and possibly how it felt to drive, gas efficiency, maybe based on safety features if she had kids, but probably not based on horsepower, number of valves, ease of repair, or how easy it is to get to the oil.
We techie people like to get all condescending with women regarding technology because they don't place as much importance on statistics and numbers like we do, but the truth is they just know those things aren't important to them. If an ugly lump of gray plastic in the middle of your living room with wires hanging out and as loud as a jet engine appeals to you then great, but don't expect that to be a selling point for everyone.
I understand she's going to be coming back and complaining that her laptop is too slow. It's the vendor's fault for not selling a fast enough laptop in pink. Don't tell her she has to make a choice between an ugly gray computer that's fast enough or a slow pink computer--tell her how she can make the pink computer as fast as the gray one.
Damn, I'm getting old.