I don't think she should have been given a custodial sentence. IMO she shouldn't have been convicted in the first place.
It's important to remember when this happened, it was back in 2020 at a time when everyone was hyper aware of COVID and the 2 metre rule etc. It wasn't uncommon for people to tell others to keep back around those times, or when you were out on your daily walk to cross the pavement to avoid passing too closely to others.
Auriol Grey is also partially blind so that probably heightened her fear, something coming towards her at faster than walking pace but not being able to properly see what it was.
It's very sad that someone died but I don't think it's her fault. To be brutally honest, the cyclist should not have been on the footpath in the first place (the fact that no one seemed to know if it was a shared cycleway is ridiculous - there's no signage to say it was, which suggests it wasn't, however the judge in his summing up said it was, and given there was nothing conclusive either way he shouldn't have done so). However even if it was a shared pathway, on seeing a pedestrian ahead should have either moved into the road or crossed to the opposite pavement to maintain an appropriate distance. In terms of the hierarchy of road users, pedestrians are the most vulnerable, so a cyclist should give way to them.