I, too, lied about something someone did to me when they never actually did it. It almost ruined their life, but I was able to rectify it in the end. However, I never told the person what I did.

I did it because of a misunderstanding (a friend misinterpreted what I said), and being forced to admit to CSA. Back in the early 2000's, it was believed if you had BPD, you had to have CSA. I was pushed so hard to open up about it. But there was none. Finally, they told me if I didn't open up about it then I was faking my mental health disorders and I'd lose all my resources including financial, housing, and counseling. So I blamed this person.

I'm sorry you're going through this. It's hard. It does not make you a bad person. Whatever the reason is you did it, I'm sure it was because it was the best option you thought you had at that time. I also still suffer from the guilt. One day I hope to forgive myself.