We're all familiar with the concept of minger but ming - dalla -ming simply refers to a particularly fine example of mingingness, a girl who stands out in an ungly crowd as being above and beyond the normal boundaries of unattractiveness. Excess hair, weight and poor skin can all contribute to this definition.
You might say "Hey those girls are pretty average, but see the one in the blue. She's Ming - Dalla - Ming!"
You might also say "Now that is simply Ming!!"