Well since my post,I have been spending a deal of time working with her coming down the step.I am making progress,and yesterday she did go up & down on her own a few times.
I messaged Deb Bauer,who owns Treasure a blind & deaf sheltie. And she gave me some ideas to try,and they worked. She did not think the nose work had any thing to do with the confusion.
She suggested going back to 101 with her,just like the first day home,when we were acclimating her to the house,still using touch,and food combined. As she ventured closer I gave a treat,and she was nervous but made the trip off the step after a long while. But she did it!
She felt,as all of you (and us) that Mia simply had an experiance that spooked her. Since her nose works overtime,she knows fully well where she is,(close to ledge of step). What ever it was,the memory & scent she has not forgtotton.
If in fact,she stepped on Oreo at the step down,we are making extra sure as much as we can to make sure he is not close to the step as she enters the room.
He is so outgoing,and loves these dogs,and he is so gentle with Mia,and very curious as well.
Thanks everyone,we will get past this little set back i'm sure.