My car ran dry one day, and I never even noticed. In my slight defense, I was in the throes of my chemical depression, and truly not noticing anything that year a lot, but at any rate, my oil drained completely out, light never came on up until the last bit was out, I suppose, and then it threw a nice rod through my engine.
This was in 1995, I believe, and a friend rebuilt an engine and put it in for about $1500.00, but man, I never went without checking the oil regularly after that, no matter what state of mind I was in.
I'd recommend she check it once a week or every other week, depending on usage, and if she doesn't know how, either show her, or check it for her.
My ex-fiance was so dumb, he never bothered to check his oil ever. I checked it for him regularly, up until the point he left me. A week after we were apart, his car ran out of oil and it destroyed his engine also.
So my advice is, if you love your car, check your oil.
Brenda