She had a blatant attraction to a female in her 'school' if you bother to look hard enough in ME3.
Here we go again. We don't know what Jack's orientation is. She was once in a relationship with a couple (male/female couple). It ended in mutual betrayal. She is not available for female!Shepards to romance in either of her appearances in the Mass Effect series. Please don't say she's bisexual as if it is fact, because it is not.