1. You take the same amount of time to get ready...but it's not a problem
Whether it's getting ready to go out for the night or for the day, you never have a problem because you were meant to be together. While you shower, she picks out her outfit. While you do your hair, she does her make up. No matter what, you are done at the exact same time. No awkwardly waiting around for you
2. You understand each other's bad days
Sometimes your roommate needs her space, and sometimes you do too. You know each other so well that words aren't usually necessary in determining when to leave each other alone. A simple look will do. Alternatively, you know when your roommate wants someone around, and are always more than willing to drop plans to stay with them because you know they'd do the same for you.
3. You know EVERYTHING about each other
You know every detail about their life and they also know everything about you. From childhood friends to pet peeves, people they've had a drunk encounter with to their favorite songs. You name it, you know it. With all the good also comes all the awkward, meaning you know when they have a weird poop or a weird scratch shows up in a normally hidden place.
4. Privacy doesn't exist
You also see everything as well as knowing everything. Any conversation you have, they overhear whether they want to or not. If you have someone over, they know. You've peed together, used the bathroom while they've showered, changed in front of each other countless times, and so much more because boundaries really don't exist anymore.
5. You couldn't imagine living with anyone else
Sure, they get annoying. But at the end of the day you wouldn't trade them for anyone else. You'd follow them anywhere they want to go, and they'd do the same for you. Because you were meant to be together, and life without them just isn't the same.