Barbara and Virginia have given some food for thought. 
I had a similar case many years ago.  (Mother had had a breast
augmentation.)  Breastfeeding started out well and continued for many weeks.
Then she would not let down at all at random feeds.  We could not find
anything that she was doing differently at those times.  
She used oxytocin nasal spray to great effect and was able to discontinue
it’s use within a very short time. She continued to breastfeed for about 3
years.  
Nowadays I would suggest rescue remedy first as it can be quite helpful.
There is also the little trick of using the knuckles to rub on either side
of the mother's upper spine (neck and shoulder area).

Jean Ridler  RN  RM  IBCLC
Cape Town, South Africa

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