I think I have a clue what you mean. But is it accidentally ? How can that happen, and is it an advantage or an disadvantage in your opinion ?
It's accidental, or rather, she cannot fully control when it happens. This is a very common problem for people with the kick serve, it often comes out with slice instead of straight kick or twist especially on the deuce side. It's quite tricky to hit up the back of the ball on the serve without coming around the right hand side of the ball, and whenever you come around that right hand side it slices or becomes slice-topspin. Her toss for the second serve tends to be a bit too far to the right for a kick serve, but on the ad side she can sometimes get away with it and still hit a good kick serve out wide. She also tends to stand a bit too upright and she doesn't really arch her back to the left enough on the kick serve (although in reality a lot of that arch is actually created by angling the entire back to the left, not so much by actually bending at the vertebrae, look at Federer's back position on the second serve, Stosur as well).
It's a slight disadvantage because it makes the placement of her second serve a bit questionable at times, often centrally placed or in the forehand side. It becomes possible for an aggressive returner to run around her second serve or predict it more easily. She cannot fully rely on her kick serve to find the backhand corner under pressure on the deuce side in particular, but this is less of an issue in the women's game where the forehands are not so big normally. It also makes her a bit more likely to doublefault, because on the second serve some of the spin will become slice instead and reduce the amount of topspin she gets.
A lot of female players can't hit a true kick serve anyway. So at this stage it isn't that big a deal, so long as it doesn't lead to too many double faults. It also shouldn't be much of an issue against left handers, because you need that slice/topspin mixture on your second serve against lefties, to get your second serve to their backhand. Also her natural slice is pretty useful on the first serve out wide.
When she gets it right her kick serve on the ad side is quite nice, but I can't remember her hitting a real kick serve on the deuce side. I think she should be able to do it though.
For an example of this tendency causing her problems, see this service game here: http://www.youtube.com/watch?v=fiNf3l2lJXA&t=40m0s