I'd go ahead and send off for her pedigree!
Even if you have no intentions of breeding her. I don't like the idea of a registry number sitting out there floating.
In either case, w/ regards to her dimensions, to get her proper height you should find her wither-her shoulder (pick the highest point of her shoulder blade) and take that down to the ground and you'll get her height. What is it now? The length of her back, measure from the base of her neck (where her collar would rest) to the base of her tail (where her tail begins). What is it now?
I've attached some pics to help you. Please disregard the unattractive Jack Russel, but he's one of the only other photos that I have that shows you the way to measure length. Now that you've got that, go for the proper height measurement. The other two photos just show you good toplines and with the way their hair lies you can see quite clearly the points you'll need to measure.