The Trek 6500 WSD has an air sprung fork with a lock out, hyro disc brakes and I believe LX/Deore level shifting bits. One of the things to look for is a shimano crank, which this bike has, it makes a big difference is shifting performance up front. This bike is one of the my picks for an entry level bike that she will not not grow in 6 months. At about $800 it is a decent deal.
There are a few people talking about upgrading and getting a decent frame. Don't worry about that. If something wears out then upgrade. Otherwise you are wasting your money. With bikes today you get a package deal when you buy them. If you buy a bike for $800 and you want to upgrade the fork, it is pretty easy to spend another $600 or more upgrading the fork, just stick that money somewhere safe and pile it up for a new bike.
Here is the situation: Two years down the road, she wants a new fork for her $800 bike. Ok so you pluck down $600 on a new fork. You still have two year old shifters, derailuers and wheels. The other way to do it is sell the bike for half of what you got it for, now you have $1000. Add another 200-300 on top of that and you get a bike that has the fork you were going to buy and a lot nicer parts that are all brand new, the frame probably will be a nice grade also. Another problem with upgrading is you get stuck in a bike, if you invest in an expensive fork it does not raise the value of the bike and you start getting more and more upside down in the bike.
I know someone who bought a bike for $500, they upgraded almost everything, spent about another $1200 on the bike over the course of a year. When we go and list the bike on ebay, everyone just sees the name of the bike and thinks it is a $500 bike new, maybe they take some of the parts into consideration, it sold for $300.
In summary, I say keep your bike as stock as possible when you are dealing with off the shelf bikes and don't become attached to them. As your skills outgrow the bike get rid of it, don't upgrade.