The mistake was for the expenses to be so high. It's because she previously worked at corporate channels that had those positions so she hired for those roles without understanding that a new channel in a crowded segment (cooking) will take many years to build an audience.

If she had done more of the work herself, it may have meant longer time between each video but more potential for the channel to be profitable.

Profitable channels, and there's not that many of them, usually take many years to get to profitability- or some semblance of being able to live off YT. Without that patience and keeping costs down while income is low, is a recipe for an unprofitable channel.