My work friend and I went for the same job, I got it…advice

Hello! My work friend and I applied for the same position which is a step up from our current role (working with ALN) I wished her luck if she was applying and she was adamant she wasn’t interested and couldn’t meet the expectations for the role. It got to interview stage and we were both there. We are really good work friends and have been for over a year, we are the only two in our position and work really well together. I got the job, which means I’m her “boss” and I’m feeling really anxious of how our relationship will be. She’s told me not to change ANYTHING which unfortunately will happen and I have reassured her I’m working with her. Things seem strange between us but I think that’s just my anxiety of the situation. Any advice for how to go about relationships with staff after a “promotion”. Also, any tips for feeling like an imposter in my new position lol?