Forbes magazine is looking into its recent ranking of entertainment’s highest-earning women after reports that Bethenny Frankel made many millions less than originally thought for the sale of her Skinnygirl brand. The Forbes list put Frankel as the No. 3 female earner behind Oprah Winfrey and Lady Gaga. Forbes said Frankel “recently sold her Skinnygirl Margarita mix to Fortune Brands for an estimated $100 million.” But press reports yesterday said that a quarterly filing in August revealed Fortune paid just $8.1 million. A source said Forbes is “taking this very seriously” and “looking into it.” Reps for Forbes and Frankel did not get back to us.