She must have SOME sort of built-in protection to prevent her from burning up due to air friction. I believe DC retconned the Flash to be protected by an invisible aura from the universal "speed force" or whatever they're calling it.It would also probably completely fuck up her hand.One tiny fist moving at Mach Whatever = stain on the wall.
She's fast, but she would still suffer from an impact.
If she's REALLY all that fast, she could do more Flash-like stunts like running in a circle to envelop a foe in a cyclonic vortex or waving her arm fast enough to generate air currents that could throw a foe into a wall or off a roof. The thing is, nobody is really EXPLORING their abilities on the show to see if such things can be accomplished in the Heroesverse.