Because Garuda is the carrier of Lord Visnu, he is the supreme Vaisnava. Therefore to touch his body with one's feet or to climb the column of Garuda is certainly a vaisnava-aparadha, an offense to a Vaisnava. The woman was also offensive to Krsna by putting her foot on the shoulder of Sri Caitanya Mahaprabhu. Seeing all these offenses, Govinda very hastily made her get down.