Join Date: Oct 2009
Location: Just south of sanity
You're correct, Indy. DNA typing is to prove parentage, not somehow figure out who the parents were.
Also as you stated, in order to prove parentage, all of the animals would had to have been DNA typed at some point, in order to match the child to the parents.
OP, if you have her registration papers, they should indicate who her parents were. If you want more information on them, contact the registry. The registry may not have anything on them though, because if they're all ranch bred horses there's no guarantee they ever did anything other than work.
What's so important about her bloodlines? You already know what they are, so what exactly is it that you want to know?