She's lived in a place full of women all of her life. Why wouldn't she have found love with another woman? And it's Greg Rucka. Rucka in on par with Perez in how much he respect history and continuity of Wonder Woman. Revealing that Wonder Woman is bisexual is fine and it's pretty much in line with a lot of Wonder Woman's crazy history of magical twins and fighting time-traveling Nazis.
Actually, it doesn't make sense at all. If the women on Paradise Island were once part of man's world, and that seems to have been the consistent portrayal, then most of the Amazons are heterosexual. Since, homosexuality runs at about 10% in the broader population. Because the Amazons were granted immortality, and existence apart from men, the implication is that part of the enchantment involves taking all sexual feelings away from the Amazons, to make eternal life apart from men bearable. Diana is the exception, since she was created much later, from her mother's great desire to have a child. But not a husband. The Amazons aren't homosexual, or bisexual. They're non-sexual, in the pursuit of a higher existence. Carnality is a male failing, in their eyes. Diana wasn't part of the original enchantment, so she's unaffected. Any love she has for her sisters is a platonic, familial love. And any portrayal of Diana or the Amazons as lesbian is more to excite young, rapacious males on the one hand, and satisfy the demands of the SJWs on the other. But, logical sense? No, not at all.