How do enlightened people experience seeing their body in a mirror?
Nothing special. The specialness of seeing your own body/face as opposite to someone else’s is no longer there. For that reason alone you actually start using mirrors much less than before.
It is beautiful, yes, but not more or less than everything else. If one is what would be considered attractive by others, there could be an appreciation of the fact, but it’s a factual appreciation, not an emotional one. Like noticing that you need a haircut.
Even beautiful isn’t really the right word to describe it. It just is what it is. Only ugliness can remember beauty.