I have a godsister that recently gave birth. She has breastfed her son for the first 3 months of his life, but she'll be going back to work soon and she wants to bottle feed him. She's pretty much weened him off of the breast (only breastfeeds at night) and feeds him breast milk from the bottle. But she's not really producing enough milk to keep him satisfied. Would it be okay to give him one or two bottles per day that are formula, or is 100% breast milk the best way to go?