In what way does Gabi's mother send mixed messages about premarital sex in the novel, Gabi, a Girl in Pieces?

Gabi points out that her mother tells her not to have sex until she is married. However, Gabi’s mother tells Beto when he goes on a date to make sure to take a condom with him. The things that their mother tells Beto as compared to those she tells Gabi about sex are contradictory, as if it is accepted for boys to have sex while girls who have had sex are treated like pariahs.