How to be a better old sister?

I (19F) want to be a better old sister, but how?
I have three younger siblings and one time we were having a talk in my room and they said they don’t feel as close to me because of when we were younger since I would be isolated a lot because of bad mental health. I REALLY regret it and I’m trying to get better and it did hurt a bit but I know it’s my fault. How can I be a better older sister? I’ve been trying to get better and they mean the world to me and I just have a lot of regrets in my life.

And they feel as if I’m just to much of over protecting or something too, and I don’t mean to do it like that I mean obviously I look out for them but I don’t want to be annoying, how do I be a cooler older sister? But honestly just a better sister overall?