Family relationships are sometimes the most difficult of all and bring up so many strong feelings in us. It doesn’t sound as if your sister is in a very good place herself just now, so you probably just have to protect yourself and politely explain briefly (as you did). In time, she may appreciate more about your needs and feelings, but I think you know you have to take care of your own recovery for now. You may be surprised later to find that she has learned from your example – but none of that is within your control, of course.
If you need to reduce your online time, I think we all respect that – everything here is to help you in recovery and when you need another way it is good that you know yourself well enough to follow your own inner wisdom. As you say, a lot of what you have learned is within you now and you can practice it.
Best wishes as always,
Monique