Which Cassie totally let slide from Kon that one time, but she started getting suspicious when Kara did it too. Although that may have also had something to do with Kara wanting her to wear a red shirt and her old black wig from her first costume...
Diana would have sex with Drunk!Artemis if Diana were also drunk, which leaves you the challenge of how in the blue hell you get Diana drunk (particularly without killing Artemis, if they're drinking together). Short of drinking straight out of the flask Bacchus keeps on his hip - though given it's Diana, that's actually an option, so there you go, you just need a reason for her to have her hands on that.
Poor Bacchus, he never gets any love. He and Persephone. Even Apollo's gotten a little page time to be a dick to Diana over the years, but the seasonal deities are barely even canon. (Which is a real screw for Persephone, actually; she should have inherited the underworld after Hades' death. She helped the Patrons back in the beginning, too, so that's a screw *and* a betrayal. One hopes Athena had long-term plans to make up for that once Ares' usefulness was expended.)