Incubus city, simply mindy or the prequel to simply mindy. Similar games as in its meant to be replayed a lot and you get bonuses that carry over based on achievements no ? Could recommend other stuff but that is not exactly lewd per se.
I'm not sure on the specifics but I think you need to have slept with both, spied on and joined Natasha's threesome with Carol and have high enough attraction with both. The option appears in Melanie's room where you ask if she likes any girls.
