Unable to feed breast milk at night freq

My baby is 6 months old Now. And she cant concentrate on her sleep at night and asks for breastfeeding everytime when she wakes upnin night. My wife is totally dissapointed as most of the time her breast goes empty if frequently feeded in night resulting in less ability of milk breastfeeded to the baby. This results in hungry baby, and not able to sleep the whole night. My baby wakes up for a minimum of 5 to 6 times in night. Now a days my wife doesn't have that much of milk breast milk as per babies drinking expectations. We have started feeding baby with smashed rice and mung dal, fruit puries, cerelac, formula milk during day time. Please guide us how to avoid breakjng sleep of our 6 months old baby girl. her weight is now 7 kgs. Reply awaited.