Summarize this article:

Recognize that men are often more overt about expressing their interest in someone romantically. Women often hint. What's her mood like when she sees you? If she becomes giddy, extra happy to see you, and full of smiles, that's a good sign. Does she ever show jealousy? If she shows jealousy, such as when you spend time with another friend, that could be a sign she's interested. Is she trying to get you alone or does she only hang out with you when other friends are along? If she's always trying to get you alone, it might mean she wants to hook up with you. Does she have open body language (body facing toward the woman, palms up, feet pointing toward the woman) or closed (arms crossed over her chest, palms down, body facing away, etc.) If you catch her making eye contact with you (you're a woman interested in her) or if you catch her making eye contact with another woman (if you're a guy or a female friend of hers), she may be bisexual. Persistent eye contact can be a way of creating intimate connection and to flirt. Also, you should pay attention to the amount of personal space she leaves between herself and other women. Is she trying to create a zone of intimacy? Looking someone in the eyes and then glancing away is a sign of flirtation in many cases. People don't usually lock eyes with people they only consider friends. Avoid stereotyping people. That being said, sometimes you can pick up clues from how she dresses her body. If she goes for an androgynous look, or something like a suit-and-tie combo, she might have a bisexual vibe. Other clothing that might provide a clue would be low-slung pants, Calvin Klein briefs, and trendy fitted blazers. Keep an eye out for rainbow accessories or pins that show she's out. Some hairstyles are more associated with being a lesbian than others, such as a barber's cut or military cut. Short fingernails could also be a giveaway. However, absolutely none of these clues is surefire. There are many bisexual women who dress differently. It all differs on the individual.

Summary:
Assess her mood and body language signals. Watch what she does with her eyes. Look for clues in her fashion sense.