While not directly proving Wonder Woman is bisexual, it has indicated that feelings towards women on Themyscira is normal. In the New 52, Hippolyta, Diana's mother, dates Derinoe, an Amazon.
Wonder Woman is bisexual. In the comics, she’s dated both men and women, most notably Steve Trevor, Superman, Batman, an Amazon woman named Kasia, and Alethea, an Amazon Stablewoman.
Wonder Woman has a history of presenting LGBTQ themes throughout her comics; she has just never been shown to have had a relationship with a woman before. One of the better-known examples of LGBTQ relationships in Wonder Woman comics is the unrequited crush that Io had on Diana.
But fans and readers have been waiting patiently for years for Wonder Woman herself to be explicitly confirmed as queer, lesbian or bisexual alongside her fellow Amazons.