M is 44. She was born in Los Angeles, her parents are from Guadalajara, Mexico. She told me about this belief about when is the best time to cut your hair so it grows longer in peron.

“When the moon is full, that’s when you should cut your hair because that’s when it will grow longer. My mom told me that.”

https://www.almanac.com/fact/ive-heard-that-if-you-cut-your verifies this piece of folklore, noting that the moon has to be waxing and not wanning, otherwise the hair won’t grow as fast. This article from the New York Times https://www.nytimes.com/2000/06/18/world/full-moon-haircut-breaks-italy-s-law.html also confirms this folklore is popular enough in Italy to cause some salon owners trouble when late night haircuts conflict with local business operating laws. For more general folklore about haircuts, see https://www.lovedbycurls.com/hair-talk/8-crazy-hair-cutting-superstitions/.