If you are concerned that your mum will not support your decision to FF perhaps you can tell her that you are feeding the bub EBM? Little white lie to tell till you feel you are ready to explain your decision to her. Otherwise maybe start talking to her now about what you are feeling and why you are thinking to go down the ff path. If she isn't supportive you might need to just realise that she is not supportive of your decisions and not listen if she starts talking about it.