How to say “She unfolded the napkin across her lap and only then saw it was stained with someone else's lipstick.” in Japanese
In Japanese
彼女、ナプキンを膝に広げたところで、それが誰かの口紅で染みのついたやつだって気づいたんだって。
Kanojo, napukin o hiza ni hirogeta tokoro de, sore ga dareka no kuchibeni de shimi no tsuita yatsu datte kizuitan datte.