My wife had a warrior, we installed a cam, header, high compression piston, carb... It was faster than any of the raptors and stock 400exs, but it was still slow and a ton of work to get up the hills at pismo. The new Raptor 350's are the have the same motor and suspension that was developed in 1984 when the warrior was introduced. Don't take my word on it, research it! The September 2004 issue of dirtwheel magazine featured a shootout between the Raptor 350, Honda 300ex, and 400ex, The raptor got beat by the Honda 300ex every drag race. (Now that is really sad!!! They are marginal utility quads, defenitly not a sport Quad. We bought my wife a 05 Ltz 400. Nice reservoir shocks, excelent suspension (I like it better on the track than my Trx450r. It is geared perfect for tight woods single-track riding (Which we do a ton of) and open duning at Pismo. All we've done to it is a DG header and silencer, airbox off and a Jet kit. It blows the doors off 400exs new AND old. Sorry that's the truth. Don't believe me just watch them run some time. It's not even close, and that is with my wife who is 5"10 130 riding it. The bike is very predictable, good power, easy to start and reverse. The only other mod suggestion I have is a rev box the stock one is limiting. I also highly recomend an 05' or newer. In 05 the ltz400 got a larger carb, reservior shocks, and a new cam!!! She rides it right with my buddies who have Yz450f's, YFZ450's and trx450rs. You're girlfriend can grow into the bike, and it is alot safer than trying to get her to climb on a bike that is under-powered. If you must go with a Honda, my wife loves my TRX450R, says it's easier to climb with because the power is so redily available. You can't go wrong with a YFZ450. But neither of the last 2 bikes get you a reverse. I bought her Ltz400, Out the Door for $5700. So argue the price!!!
Best of luck with your choice.