I'm torn. On the one hand of course having to step back for medical reasons (be it herself or her partner) is nothing to celebrate and I obviously wish her the best - there's absolutely nothing to celebrate about someone going through something so bad that it requires them to leave their career.
But that being said, she'd have either been pushed out, or become CEO at some point, and the former is by far a better result given her views and comments on certain areas of the business. She's a numbers person, not someone with enough vision or leadership to run a company like Disney.