Rich - cdi was right on the measurement - as far as bits - like another poster said the previous owners probably knows what works best for the horse.  I would look for an older horse to get her started.  Something bomb proof - take the dog with you when you go look at the horse.  Walk away from anything you not sure of.  The lady that is teaching her is probably an excellent resource. Good luck.

My wife has had horses all her life http://www.alwayswalkin.com/showhorses.htm I used to thank her dad constantly - just like I am sure your future son-in-law will do to you!