I also think that if a six-month old is crying every hour, it is more likely that he/she is nursing for comfort rather than out of hunger.
It is tiring for your friend but if she has no complaints, there is probably no urgent need to advise her to do anything else. But if such hourly feeding schedule is tiring her out, you can highlight to her to note how much her baby is really drinking at each feeding. She can then determine if her baby just wanted to suckle for comfort. If that is the case, you can suggests to her to try other methods to comfort her child. She could also get others (husband, or other family members) to help with the comforting so that she can get more rest.
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