To be sororal is to be sisterly or sister-like. If you crave sororal company, join a sorority...or a convent.
A sorority is a college club for women, and the young women in the same sorority call each other sisters. Similarly, acting in a sororal way is to act like a sister. Two women who look like they could be related have a sororal resemblance. Even fighting could be considered sororal, since sisters don't always get along. This word is similar to fraternal, which means brotherly.