Thank you for your query.
Your daughter is gaining weight adequately as a child should gain 500-600 gm. per month. Hence, seeing her birth weight
her weight of 3.86 Kg at three months is absolutely fine.
At this age you should not be extracting the breast milk and feeding the baby. Let the baby suck herself. The reason why she is not able to suck is that she is having nipple confusion while feeding both from a bottle and breast. If you are keen to breast feed then you need to give the supplement feed with a spoon or with a bottle in which the nipple has a very small hole.
Regarding the quantity of the supplement milk being fed to the baby, please do not take the instructions on the tin literally as every baby has his/her own requirements and frequency of taking feeds. Secondly, the instruction is for an average normal baby weighing around 2500-3000 gm. at birth.
I hope I have answerred your query to your satisfaction.