Oh, so it's like cheating men must die, but the protag is way less experienced.
I must say, texting him to blackmail him was really stupid though. It'd be really easy to twist the story into saying that the MC stalked the purple-haired person and took a picture of him naked, then attempted to blackmail him using that photo. It'd make the purple-haired person lose some pride or whatever, but his career won't be ruined or anything.
Of course, the MC has the audio recording of him drugging her, but that in of itself is suspicious, since it would be hard to explain why she started recording someone in secret while having a drinking competition. The purple-haired person can claim that she hired a voice actor (and he can probably frame her by framing someone else to take the fall) to sabotage him, and that he had no idea she was such a person.
The bartender is also a problem. He probably won't advocate for the MC because the drugging was done in secret, so he likely doesn't know about it. What wasn't secret is that the MC knocked out the purple-haired person with an ashtray. That's straight up assault with a witness. Maybe he'll get flamed for being "weak" or whatever (because that's how media works I guess), but he could just claim that he was bewitched and tricked by the MC.
Additionally, there are plot holes that make it really hard to enjoy the story, like how the MC suddenly acquired video evidence of her best friend saying "I only think of him as a brother" or why the purple-haired person tried to stick up for the MC (even if it's fake). Yes, he did it so that he could get on the MC's good side to sabotage her later, but he could have done that too by "comforting" her later and inviting her out to drinks to help her "cope". There was no reason to save her from the bitch slap.
I'm hoping that as the story progresses, the MC gets smarter with her tactics and starts using the system more cleverly and efficiently, but honestly, the prospect isn't looking so great. At least the art is cute.