Then again in the last panel she is sleeping with Yeonwoo. He has the ring on his hand and you can see the tattoo on his shoulder(⊙…⊙ )
I think she's just hallucinating or like imagining him doing it with her but it's really the friend
I thinked that to after i read it again ┑( ̄Д  ̄)┍ we'll see
Then again in the last panel she is sleeping with Yeonwoo. He has the ring on his hand and you can see the tattoo on his shoulder
(⊙…⊙ )