I looked your mare up on APHA's plus website. She is APHA registered. Her last ownership transfer was dated 5-20-07. I know they are slow this time of year with new foal registrations, but I do hope you have sent in the transfer.
I also think you may have confused ApHC with PtHA, so I tried to look her up with PtHA (pinto) I could not find her under the name you gave. It is possible they chose another name at the time of registration. I will note that her sire, ImpressiveCredentials, is PtHA registered. The pinto system doesn't let you do pedigree research, so I could not see a list of his foals to try and find your mare.
You should check with the people who gave her to you to see if you need to transfer PtHA papers as well. I would also strongly suggest you get the HYPP test. Knowing her status is crucial to the mare's health.