Are they standing far away from each other or far away from another object?
I'm pretty sure from each other would be 우라는 서로의 멀리에 서요
The sentence is they are both standing away from something. But I think it is actually wrong. 멀리서 or 멀리에서 is fine but 멀리에 doesn't make sense. Standing away from each other would be 우리는 서로에게 멀리서 서있다.