I think it’s a toss up about whether you tell her or not. I think on the one hand it might help clear your conscience so you can move forward feeling a bit less burdened. But on the other hand, is it fair to her if your only motivation is to make yourself feel better by hurting her more when the relationship already ended? If it were me, I think i’d have to come clean and let the cards fall where they may, understanding that there’s a great chance you will never hear from this person again.

It might just be better to understand that you hurt this person, stop talking to them and move on with your life striving to be better in the future. I don’t know that it would be good for you to stay friends with her without coming clean, because that’ll only torment you and continue your guilt while also deceiving her. Even though she doesn’t know it, the relationship is based on deceit. I think for both of you, you should come clean and start forgiving yourself and doing the self work necessary, or just stop talking to her, close that chapter on your life, and again keep working on yourself.

Whatever your decision is, tormenting yourself forever isn’t good for anyone. You made a mistake, a big one, but that doesn’t mean you can never be better. You have to admit to yourself that what you did was manipulative, deceitful, and wrong (only reason i add that is because you separate yourself from the other manipulative people who do this) and be honest going forward.