Who is Jenny 'Ma' Grier from The Ox-Bow Incident and what is their importance?

Jenny Grier, or Ma, is a local woman who runs a boardinghouse. Ma is known by her nickname because she often cares for the men when they come in from long months of watching over the herds. Ma is well respected in town and thus becomes a leader in the vigilante mob. In fact, Ma is one of the people who executes one of the suspected killers by urging the horse under him to run. Ma encourages the mob, using words to propel them on, becoming a part of the mob mentality.