My daughter fits that description, although is a few years younger.
We are on Facetime several times a day.
I talk to her on the phone whenever she has to walk anywhere.
I help her by speaking to professionals with her and on her behalf (often when they have written permission from her).
I help her to plan meals, work out social issues, write emails, remember tasks.
I encourage her when she is putting off things that are hard to do.
I take calls when she is struggling in the middle of the night.
When she comes home, I help by giving her a break from the executive function she finds difficult by planning and providing meals, working out what is happening when, washing her clothes, etc.
I also tell her how proud I am of her and how brilliant she is for what she has achieved because it is so much harder for her than it is for her peers.
I actually spend more time supporting her than I do her much younger sister who is at specialist residential school during the week and has adults at her beck and call 24/7.
It is hard work always being available but I know she would fall to pieces without it and I also know that she is very gradually taking on and managing more and more for herself. I isn't going to last forever.
Happy to chat by PM if it helps at all.