For me this situation is not really comparable with an abusive coach/student relationship, cause Aljona was not Brunos coach obviously, but we're talking about 2 adult partners.
They were equal partners from a power balance point of view, not coach-student, not adult-teenager.
Ingo certainly was abusive to Aljona and Bruno (and Mandy) and probably countless others, so basically Aljonas whole career was formed by toxic coaching relationships, which was written down in books, even before Bruno teamed up with her. In comparison to Aljona/Robin/Ingo her partnership with Bruno seemed a huge improvement, at least after they moved to Alexander Koenig, but of course she's a ruthless competitor and a very complicated partner, but from all that Bruno said over the years and how he spoke in the documentary, he's probably not the most uncomplicated partner either. They both sounded "interesting". And if I recall the documentation, they indeed considered quitting at some point.
And no, MsZem, Bruno did not train in Chemnitz before he skated with Aljona, I think that's a mixup. You're probably thinking of Robin?