Have you had her try out your G9 for size? Not specifically for the G9 but just to see if she has an easier time manipulating the dials or the buttons (G9 has both). Then have her try out a subcompact (your D-lux3??) and see if she has an easier time with the compact body or a larger bodied G9. That should give you an idea of what design to consider.
My lumix TZ5 for example:
* 10x optical makes for less foot zoom.
* Big LCD screen
* Built in handle
* The main function selector is a dial on the top of the body.
* If you place the dial in iA mode, it is completely automatic. It will switch between modes (action, landscape, face recognition for portraits, flash, ISO select) automatically. It places a box and tracks a persons face to make it very easy to confirm focus for portraits.
* Turning the camera on and off is a physical sliding switch instead of a button
* Moving between display and record mode is also a physical sliding switch instead of a button.
* Almost the entire operation of the camera is via the dial or the two physical switches mentioned.
* There is a button on the top of the camera to automatically zoom all the way in or all the way out. Might be a little easier than holding the zoom selector left or right.
Now the bad points, the buttons for other features are small. The TZ5 is a superzoom but compact in size which might be hard for older hands to hold steady. The SLR like P&S with a large built in handle might be easier but also might be too large to carry.
These are all me just thinking out loud and not really sure. I'm just speculating that the sliding switches might be easier than the buttons.