If you have a plug you could use, the HSM 200 is often used as a night light and you can programmatically change the colors so it also makes a good indicator light. You might be able to put it into a Outlet and Then put a clear plastic project box over the entire light and outlet to protect it if you think she would pull it out of the wall. Just choose one that’s ventilated so it doesn’t overheat. Open parentheses a “project box” is used for electrical projects. You can typically get them at Amazon, Home Depot, or any electrical supply store.)
I believe it has a choice of 8 colors all together. There is community code for it and several community members using it.
It would also be really easy to add daisy petals around this if you want to make it more decorative. 
If it absolutely has to be battery powered, you can get a standard battery pack and plug it into that, but to be honest it would probably be cheaper and easier just to have an electrician add an additional outlet higher up on the wall. Since I’m in a wheelchair, I’ve done this in several rooms, and some older people do it as well so they don’t have to bend down so low. 
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