The one problem every Blast has is the rocker gasket -- it´ll go between 6000-8000 mi. It´s a quick, cheap fix. I´ve heard a lot about mechanical problems with this bike, but I´ve had mine 2 years, and the only troubles have been the rocket gasket and the head gasket -- which went because a REALLY push my bike hard. I´ve seen a few people that have had trouble with leaks at the fork seals, but I´ve not had that myself; in general, those bikes were not well-maintained.
If you take care of the bike, the maintenance -- I´ve found -- is bulletproof. I do recommend you change the exhaust for an aftermarket pipe -- it gives you about 5-7more horsepower. If you want to ride for distance, I´d also investin the Corbin gunfighter seat made for her.