Thank you for your query.
I hope I have understood the problem properly:
1. The baby is waking every 20 minutes to have mother's feed and this has been there from birth
2. Her weight gain is adequate
Presuming the baby's weight gain is appropriate for her age then I shall not worry about this behaviour. It is very common for babies to have the comfort of their mother and would latch to her frequently. However, this is the appropriate time to dissuade her from night feeds. It will be better to give her some solid food before she retires so that she does not demand a feed in the night.
If it is correct then it is Cypon
drops which is given to increase the appetite. If you have not started giving the drops and the weight gain is adequate then there is no need of giving it. If you have been giving it then the above behaviour of demanding feeds frequently can be due to it.
I hope I have answered your query to your satisfaction.
Wishing your daughter all the best.