They are enjoying nursing and are not ready to quit. She also has a two older children who enjoy her attention at bedtime, so by the time she has them settled down she is exhausted. Just putting the twins to bed and letting them cry is not something she is willing to do. She is a Board Certified Lactation Consultant, as well as a retired La Leche League Leader. It can be helpful for your friend's babies to begin to learn other ways of relaxing and settling into sleep.
Fathers can be very instrumental in helping their babies to learn a new sleep association.
Dad can help them to learn that they don't need to nurse to fall asleep. For several days to a week, Dad may find himself challenged in the evening. There may be some fussing and crying in the beginning, but Dad will be there, comforting the babies and assuring them that all is okay. You didn't mention the sleeping arrangements. If they are in the family bed now, begin easing them out of bed gradually, starting, perhaps, with a futon or sleeping bags on the floor, next to their parent's bed.