I'm sorry for that loss :/ Dobermans have always been another breed of interest for me. Koda's first same-age playmate was a dobie puppy at the dog park when she was 8 weeks. Poor thing's ears were taped from being cropped xD
If you just keep working at it, it's possible to move through it (: Trust me, I've been there. Try a head harness, LAT, and lots of "Focus" obedience training. When Koda reverts a bit and bristles, I just say "Eyes on me," and she's back paying attention to me and ignoring the dog.
Mom To~ Dakoda (b/t GSD), Simi (b/w DSH), Nashoba (sable GSD)