Who is Peach from Lonesome Dove and what is their importance?

Peach is July Johnson's sister-in-law. Peach got her nickname from July's brother and it's a name July has never understood. An overbearing woman, Peach is controlling and not afraid of anything or anyone. When Jake Spoon accidentally shoots her husband, she bullies July into going after him although it's against July's better judgment as sheriff. Mary had met Ben in Little Rock, and he had been so smitten with her that he even stayed there two months to court her.