A Penn State sorority is facing an investigation after posting an offensive picture to social media, Onward State reports. The photo of a “Mexican-themed” Chi Omega party that surfaced Monday [1] shows a group of girls wearing sombreros, ponchos and fake moustaches and holding signs that say “will mow lawn for weed + beer” and “I don’t cut grass, I smoke it.” The girl’s identities were discovered because they were tagged on Facebook, Onward State reports. The offensive photo led the Penn State Penhellenic Council to investigate [2] the Nu Gamma Chapter of Chi Omega, according to the online version of the school’s paper, The Daily Collegian…