Er det ikke bra, norsk trevirke?
Isn't it good?
Will the meaning different if it were "rommet hennes"?
From my understanding "hun viste meg rommet sitt" means that she's showing you her own room whereas "hun viste meg rommet hennes" would mean that she is showing you someone else's room.
I could be wrong though, my Norwegian is still very basic.
Basic? More like perfectly correct. :)
"...and then she said it's time for bed."
Norwegian Wood-The Beatles, 1965