Brewer's: Gay Girl
A woman of light or extravagant habits. Lady Anne Berkeley, dissatisfied with the conduct of her daughter-in-law (Lady Catherine Howard), exclaimed, “By the blessed sacrament, this gay girl will beggar my son Henry.” (See above.)
“What eyleth you? Some gay gurl, God it wot, Hath brought you thus upon the very trot” (i.e. put you on your high horse, or into a passion).