First, not all moms can feel letdown; other mothers feel letdown sometimes but not others or find it changes over time. So, the lack of a letdown doesn't mean she isn't making milk.
12 days old is about when a growth spurt is expected, so feeding more frequently than usual isn't abnormal. Basically, the baby is putting in an order for more milk. Some babies will nurse every 15 minutes for a few hours at a time! The breasts are never really empty. There is always some milk there. By taking out more of those last few drops, the baby is telling the breast 'I need more!' and after a couple of days the breast makes more.
That said, nursing every two hours isn't abnormal for a newborn even if he always does that.
So, if the baby is growing (she would know from her pediatrician), making 3 poopy diapers per day, and looking well then I would say what she is describing is normal nursing. Even wet diapers can be misleading, because with the new high absorbancy disposables they can seem dry even when they're wet. So, look for poop. If this is normal nursing, introducing formula would be a mistake because right now is when that baby is supposed to be putting in his milk order. If your friend supplements now, she could have supply problems soon.
If she's fighting a mom who isn't supportive (or even if her mom was the most supportive person on the planet, truth be told), she would do well to get in touch with a breastfeeding group (e.g., La Leche League, or a group affiliated with her hospital/birth center). She should definitly talk to a La Leche League leader (many are available by phone) or a lactation consultant, as well as her pediatrician, before supplementing.