Wii Fit Trainer takes precision to master (like Marth I think he/she has sweetspots on their moves). Even yoga needs to be precise after all. His/her down tilt can also be very useful for dodging attacks. Keep up the work. :)
I know all too well how good she is on the battlefield. I played someone who used her effectively and got my butt kicked in the early days of the game haha. I suck with her though .-.
PS. Looking forward to battling your Wii Fit Trainer someday :P