sudokus and Netflix are good time-fillers (as I well know) but maybe she could do with something bigger than that - after all, she's lost the mainspring of her life. If I lost my OH I wouldn't plan on filling the gap with sudokus.
Does she have any interests from the past that she'd like to take up again? Would she like to travel? (Not necessarily abroad.) Do something with U3A? Work in a charity shop? These may perhaps be a bit much for an 80yo; then again, she might appreciate something that gives a focus to her life rather than just passes time.