It was in press materials and interviews prior to release. I don't think it was faking so much as just using Kate's attraction to her as a way of throwing her off her game because that's what Selina does with everyone.Is she openly bisexual? Is that something Weisman clarified on his site? If so, it's a failing he had to make it canon after the fact. The way Selina treated Kate here made me believe she was faking being bisexual to mess with her. It doesn't play like she's actually bisexual at all.