Was my response "incredibly mean"?

She's been drinking a mug of black coffee with me in the mornings occasionally. I have a drip maker that I put 4 teaspoons Maxwell House in. Nothing beyond that.

I got this message around 11AM. We drank the coffee around 715-730.

I get that I wasn't exactly the most sensitive I could have been, but I'm a rural mail carrier. I had to respond while stopped at a mailbox and we are GPS tracked. I get in trouble if I spend too much time stopped.