Backbiting: what are the consequences?

Hiiii! I’m a 16 y/o girl and a couple of years ago I found out that gossiping/backbite was haram, to be honest I didn’t know about it before and sinned unknowingly but when I did find out I did my best to stop. Now my question is do I still have to tell the people that I have wronged about what I have said if they don’t know and that I did it unknowing that it was a sin? And is it different if i just gossiped about them or if i backbite them bc i have seen some people say that if you gossiped about someone and they don’t know, you shouldn’t tell them and with backbiting some people say you don’t have to tell them if they do not know while others recommend you to tell them. And there is some people that i genuinely don’t remember that I have backbit? What should i do and how should i repent? And I have heard that sins committed out of ignorance are pardoned but I saw somewhere that it wouldn’t take all the consequences from backbiting (I don’t think it applies to other sins but idk I’m not a scholar). And to give more context I have done my best to ask forgiveness for the backbiting I have done to those that I remember but there are 1 person I remember I have backbite/gossiped about though I did it out of anger and ignorance (we have made up without realizing/ apologized ) and frankly I don’t think she want to know speak with me since we both will soon start high school in different schools. If it helps I have sincerely regretted what I have done and have spoken good about her when people said something negative about her or when I talk about her in general, I’m not sure she will add me back since Snapchat is the only way I somewhat can contact her. What should I do