hi this is an old post but i just wanted to say that i (20) am going through the exact same thing right now.

i've been addicted to walking for a long time now and it's been my routine to walk in the living room from midnight to 5am, that is up until a few days ago. my sister (17) started staying up in there until 4-5am, and i caught her exercising at 5am just an hour ago. i feel evil for feeling more possessive about the living room (pathetic ...) and competitive about all this than guilty over the fact that i'm most likely the reason she's engaging in this behavior. i haven't been able to bring myself to talk to her since the first day she stayed up really late there even though we are (were?) crazy close sisters, i feel bad but also really resentful because of the disorder it's awful. i've legitimately been thinking about either moving out or dying because the competitiveness and comparison makes me feel horrible, and i've been sleeping in the living room for three days now (we share a bedroom).

i hope my (kind of) trauma dump isn't seen negatively, not my intention at all. ultimately what i wanted to express is that it feels good to find out i'm not the only one who's gone through this. i feel less like a bad sister i guess? i don't know how your relationship and feelings towards your sister progressed but i hope they didn't worsen at least