Mmmm strange, it's very linear in theory. Once you put the aphrodisiac in the glasses just go out in the backyard to start a new scene, Doesn't it happen??
Maybe I found the reason why it happened: I bought the aphrodisiac when I went to get the Christmas dresses first, I got back home and I gave the dresses to everyone, then I saw Rita in her room and the girls in the backyard, then I saw mom and aunt, I went back to the sexy shop and I bought the item I needed once again, then I went back to the ladies and I put the aphrodisiac in their glasses. Finally I got back to the girls and nothing happened.
Second time things went ok: I went down to the ladies, talked to them, went to sexy shop and got the dresses, gave the dresses to everyone, first scene between mom and aunt, bought the aphrodisiac, went back and put it into the glasses, went to the gals - snowballs event, and so on.