manchester united beat their rivals city 4-2 at old trafford on sunday .
louis van gaal celebrated the derby demolition at wing 's restaurant .
van gaal was snapped with city 's toni duggan and isobel christiansen .
city striker duggan uploaded the snap to instagram of her with van gaal .
england women 's international duggan later deleted the post .
juan mata , daley blind and ander herrera also celebrated the victory .