I just discovered this newly translated Netorase Doujinshi and absolutely love it:
Takane no Hana e no Kokuhaku Seikouritsu wa Zero no Wake/Why the Unattainable Flower's Confession Success Rate is Zero (Author: Fan)
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WARNING/SPOLERS: This probably isn't for everyone since the girl was already a huge slut who sleeps around when she started dating the MC and the guy just kind of accepts it but I personally love how she isn't mean about it and genuinely tries to be a good girlfriend. I also like how even though the sex scenes are pretty extreme, the guys she usually fucks are nice guys who are genuinely happy that she gets a boyfriend who accepts the fact that she's a bitch.
It may not please everyone, but for those who like slutty heroines, this one is pretty good.