don't waste your money on the air cooled version they really are gutless, if you want to go for a 50 buy a water cooled one and fit the air cooled clutch, it has different springs and take up is much more linear. The water cooled bikes use an auto clutch with cupped washers and can be quite vicious where as the air cooled bike has coil springs.
Another option worth considering is to get her straight onto a 65 either up to 08 or 09 on the difference really is in the PV which gives the later bike a touch more midrange although this is offset by a much lighter throttle so can be quite intimidating for a new rider where as the bike up to 08 although having a narrower power band has a slightly heavier throttle action and combined to altered gearing will help build confidence. All my sons started on either Husky 50 or KTM 50 then quickly moved to the KTM 65 by 7 bar one who wanted a Kawasaki to learn on, the pre 09 KTM is a good bike to learn on albeit with different gearing I recommend 46-47 tooth rear sprocket to take the edge off the acceleration. that a few $ spent on springs will go along way
This is a video of my youngest 9 at the time just after a big crash on the first TT (jumped too big and crossed the bike up on landing) and his older brother 10 who had his first ride on an RM85 and infact his first ride in 2 years. The KTM is running 47 tooth rear sprocket. BTW he's wearing the white A* body armour and bro is in Fox Acid kit on Yellow RM
The boys at Churchills MX - YouTube