If she is indeed so careless as to use a Li ion beyond specs after explaining the Li ion safety 101, better stay away from that and get a nice looking light with AA or AAA cells.
But before you rule anything out, just explain the dangers and how much a decent cell cost and surely she will do a weekly check of the cell, as does my wife since she understands about the importance of it.
We watched the mhanlen video about the BLF special of this and my wife really liked the looks of it. I had just ordered two via the groupbuy 3rd batch produced!! GBGB: 2nd batch of BLF-348 (Classy and Small 1xAAA Stainless Steel light, with Nichia NVSW219B-V1 R9050)! and she was totally OK with that.
http://www.gearbest.com/led-flashlights/pp_227505.html