Milking her out is fine , you have to ask why at 3wks old have the lambs stopped suckling one side , is the ewe letting them suckle ? is the teat sore or cracked ? no heat in the udder are you 100% no mastitis . You need to watch and study whats going on . I know its not easy but if you separated mother and lambs for a couple of hours then put them back together you would then know .