Someone who is known for constantly backing out on
plans ("flaking"), often for reasons that are
flimsy and/or somewhat insulting ("frosty").
"My friend was supposed to come visit me in the hospital after my round of chemo, but then she called at the last
minute to say she couldn't afford to waste her gas on the drive up. I
don't know what I was expecting anyway, she's totally
frosted flakes."