Have to agree. I really, really wish Berna would take off that collar and stop liking the idea of being a slave so much. She's both traumatized and has horrible memories of slavery... yet she's happy to be one. It just doesn't fit right to me.
I know the mangaka probably just wants the focus on the rom-com hijinks, but they do occasionally keep touching on it. Plus it's hard to block out that fact entirely when reading it.