Use the K.I.S.S. method (Keep It Super Simple). Not really pushing Maglites but this is one use where they fit perfectly and I'd suggest a model or two.
First suggestion would be a plain old Minimag LED but with lithium AA's. Cheap, simple, tough, and readily available. 97 lumens so it's bright enough but not blinding. Weighs almost nothing (about 4 ounces/117 grams, including alkalines). Super easy to use - no multi modes, just an easy twist on and off. Learning to use the candle stand feature is easy even with arthritic hands - when the power goes out it will be much appreciated and also far safer than using candles (just remove the top of the flashlight and it can be used as a base for the light - the bare LED functions just like a candle). Will still work after it's been dropped and able to have a lanyard attached via a key ring. Fits in a pocket, purse, and can come with a clip if needed. Small enough to carry but not so small to be easily lost. I think the Minimag Pro would be too bright for her use (claimed 274 lumens) and the AAA Minimag would be too small for her to use comfortably.
Lithium AA batteries cost a bit but weigh nothing, have an incredible shelf life, and plenty of power. I've never heard of lithium batteries leaking like alkalines do. Most older persons aren't going to want to deal with rechargeable batteries.
No, a Minimag is not fancy or the latest thing. That's why it's a good choice. Many older folks especially those with mobility/agility problems aren't likely to use a flashlight they deem too complicated or even worse "too special," so something simple will actually get used instead of being tucked in a drawer and forgotten.
As for a 2 C cell light, the Maglite ML25LT operates exactly like a Minimag (including candle stand feature). It's about the same length as a Minimag, and with alkaline batteries weighs a little over 11 ounces/317 grams. It's not big and heavy like most C or D cell flashlights. Since it might be easier to use with older hands this would be my choice for a flashlight in the home. No hole for a key ring/lanyard and too big for a pocket though but just leave one bedside or on the kitchen counter.
Both of these lights are inexpensive enough that you could purchase multiples of them for the price of a single light from. other brands. Here in the US you can buy 4 or even 5 of either of these lights for a total of about $100US and that's in brick and mortar stores, not even online. Extra lights in the house means not having to search as long to find one when it's really needed.
