It may be her "cupcake" event. It triggers randomly at night. Idk if you need to sleep or what but that might be it. Make sure you get her added to the home harem tho. Hope this helped.
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maybe there's a bug in that case. I'm saying this due to experience. Old saves can get messed up let alone a 1year save. Hell when I updated to this current update a second icon formed implying that old stuff from my previous game was drastically changed and so far it's proven true. Hell I didn't even know Minami had a couch fun scene until this update and the "cupcake" scene was something I recently found. I recommend doing a new game with the goal of getting the full home harem mainly for Sam to test this out. If it works that's your answer.