I really dislike the trend for using victim impact statements in this sort of case - implying that the crime is worse because the person had loved ones who were affected - so, if the person had been without family and completely friendless, that would lessen the crime? No, it wouldn't.
Given the driver's life has also been changed irreparably by this woman's actions I think it's entirely appropriate for the impact on him at the very least to be considered.
As far as I can see nobody's reporting that she was even accused of pushing the cyclist off her bike. I suppose that could just be inaccurate reporting though.
BBC articles from last week reported that she said she 'believed she'd made light contact'.
'Pushing' is a deliberate action - and she'd have probably been charged with murder or at least given a much higher sentence if that was suspected.
Murder requires intent. I think they'd have struggle to prove she intended for the cyclist to die. Not giving a toss/being reckless to the fact that pushing someone into the road might be hurt isn't the same as actively wanting to kill/severely harm them them so I assume manslaughter was considered the appropriate choice in the circumstances in order to secure a conviction.