I like her conformation. She should work a cow or rein, BUT....
When you said 'high level' reiner, her pedigree kind of lost me. Since the initial investment is the smallest part of what you are going to put into her, I would be looking for one with close-up reiners. Great grandparents have a lot less influence on ability than parent and grandparents, particularly parents.
The high level reiners separated themselves from many of the cowhorses and cutting horse lines a few years back. The low head carriage (with their shoulders up) and the round, totally committed stops are just bred into them. You see fewer and fewer high level reiners that are strictly cow-bred.
She should make a really nice horse. Making a really nice reiner may be something else.