Ok, so someone else is looking after and feeding baby all night? I've not come across such a set up before. I'd be very careful you don't damage your supply if you aren't feeding frequently at night.
It could be that your baby is doing something called reverse cycling. Normally it happens when mum is busy or at work in the day and baby misses out on the comfort, affection and interaction of breastfeeding so they make up for it by waking and wanting to feed more frequently during the hours mum is around. That's normally in the night but would be in the daytime for you if it's nighttime that you aren't breastfeeding. It's just baby's way of getting what she needs from you.
