I wasnโt quite that bad when I was younger, but I did ban myself from credit cards after a certain point of wrecking my life. It has been a few years since my life fell apart, but it has literally been just the last few months that my credit has finally recovered after being unable to pay my student loans for a while due to circumstances out of my control, being bad with money due to untreated ADHD, and general I fucked up.
The thing that helps me the most is paying all of my bills from my Bank app (โBill Payโ). This way I can see the dates, setup any automated payments, and in a lot of cases receive the actual statement in the app. Having to go to a bunch of websites is stressful and if I have to mail it myself, I am screwed. Having one app/website is a lot easier to handle. I am not perfect, but my wonderful landlord only has to remind me once in a while if I forget instead of all the time. I am exceedingly lucky right now to have my finances under control where I can comfortably schedule my rent to be paid automatically without me having to worry about payday and such. It took forever to get there.
You are a wonderful person to try and help your friend. I would have loved to have someone like that in my life a decade ago, but I somehow made it anyways. Trying to get my shit together is a huge struggle and I really feel for her.