I counted 23 slips in the cup in chapter 5. The first time, our top girl grabbed the slip from the other girl so it doesn't count. So that's two times she's been chosen the slip in a row.
But that's not just it; the second pick was out of two. It wouldn't have mattered which one who was picked since both of them would have had to kiss and there's no differentiation between the two.
So the odds are: 1/23 X 2/23 = 0.38 % of the chance. Highly unlikely, but not within the boundaries of impossibility.