help for a friend - baby only takes one side

My friend just had a baby and the baby will only latch one side.. She has tried to switch positions and it won't work.. Football, etc. The baby screams her head off and will refuse one side! She said it got so bad the other night that the baby worked herself up so bad she wouldn't even take the good side for over an hour :( any advice? She doesn't want to give up BF!