The PIL visited last weekend, and MIL made a comment of "I should really drink more, I get terribly dehydrated when I'm not at home"
I said I find that too sometimes, and then she said "I just spend all day drinking weak black coffee to make sure I drink more"
I said that a headache is often one of the signs of caffeine withdrawal, she just stared at me blankly and said that it can't be that because the coffee is weak (but not decaffeinated) so the 10 or so cups she has per day can't really have an effect.
I'm doubting myself here, but she's slightly deluded, isn't she?