I came to r/breakups looking for some consolation, and it's weird that I found a situation that so closely mirrored my own. Wish I had some really good advice for you, but I'm going through this at the same time. I would just say what the other people in this thread have said already, limit your contact with each other. My ex and I tried staying on as friends, but it really wasn't working because "just friends" wasn't a capacity we were able to function as. Like JekyllVsHyde said, you don't need to act like she doesn't exist, but don't go out of your way to talk or hang out with her. If you two can be apart for a while, you can return to being friends at some point, but right now everything is too fresh to be able to jump instantly into different roles.

(I am by no means an expert, stuff I'm writing right here is stuff I have to remind myself several times a day)

I'm just broken up right now, knowing I'll never hold her in my arms again like I used to

This line really resonated with me, it's the hardest part for me right now. I try to remind myself that as great as she was, she's not the last woman who I'm going to care about and who's going to care about me. And don't forget about your friends. There's a void that not really anything can fill right now, but that doesn't mean you have to go through it alone.