Our customer like that wants her 1/4 strength decaf capp heated to 90*c (194*f) and sends it back time after time after time if she doesn't think it was hot enough.
I have told her that she needs to find another coffee shop to make her drink as I don't want to ruin my milk or coffee; and I fear that if she spills it on herself (she's in her late 80's) that she'll burn herself badly.
This only made her come in more and more. She is like a pest that thrives on annoying us..
The solution; Hold the mugs handle under the tea water spout on the machine until it it too hot to touch and she then thinks that her coffee is hotter.... sensory overload on the old ladies weak hands.... :)