I believe your friend will find that she has a baby who prefers to sleep and therefore finds it easier to take milk from the bottle ......if the babys mouth does not open wide enough to take both the nipple and behind it thats when the nipple gets sore ....often women with full breasts face this problem ......i know midwives now try to discourage the old practice of gently sqashing the breast just behind the areola between two fingers so that more of the breast goes in but it does work .......

time, peace and quiet and patience plus nipple sheilds usually helps

At least she is giving the baby breast milk not cows and risking milk allergy as so often occurs