You need to buy the Wine from the Shop in the Mall then gift it to Anna in the kitchen (it can be any day), after having sex with her for the first time there's a random chance when you go into the kitchen that she'll be drinking wine and tell you that she's horny, but just ask her if she's okay and she'll send you away, you'll have to repeat it 2 more times, at the 3rd time ask if she's okay and say you won't abandon her (or somethine like that), she'll be cured after that.
I'm not entirely sure this is how you get that star but it's something that might be necessary for it, either way I can try to help you if it doesn't work or if you need more help.