This is true, but Victoria's behaviour towards Wilhelm was pretty grim. Wilhelm did have his good points (maybe not many, but he was far from being a complete monster), but Victoria concentrated on the bad (much as her mother did with her brother), and in addition Wilhelm had all that unpleasant and ineffective treatment for his withered arm. In the circumstances it is hardly surprising that Wilhelm, who, unlike Edward, succeeded while his mother was still alive and so was in a position of power over her, did not get on with her.
It sounds as though Victoria jr could be very hard to live with - Alice of Athlone hints at this. Heinrich was of a much more 'easy' disposition than Wilhelm; he was fully able bodied and he was not the heir - his relations with his mother were always going to be easier.
Ann