[header] How to tell if another woman is bisexual [title] Notice whether she shows open appreciation for women. [step] If the woman seems to generally appreciate women, including their sex appeal, there is a chance she is. Does she always notice other people's looks and comment on them in a sexualized way? [substeps] As with every potential clue, it's possible she is just admiring another woman without having a sexual attraction to her. 
After all, women are constantly scrutinizing other women's appearances. However, if she repeatedly openly admires another woman's sex appeal, maybe she is open to more.