When I first went on the birth control linessa I was unusually irritable really simple things drove me nuts. I have never had PMS and am generally a very calm person. I found out it was because of the amount on progesterone in this particular brand. I was switched to a different kind and haven't had a problem since. (I also had nausea and cramping with the linessa it wasn't fun). I was also told it isn't all that uncommon for people like me who are normally fairly level emotionally and don't tend towards one end of the spectrum to have this kind of reaction as the body is introduced to more hormones which can have an impact on mood.
So I would't go saying it is completely impossible. I would reccomend she talk to her doctor about switching to a different pill it is a trial and error process to find one that works best since everyone react differently.
side note- my friends didn't just suddenly notice me getting nasty i noticed it myself and did not like it. I always believed PMS was an excuse for girls to be mean but I quickly discovered when you have hormones messing with your moods it is incredibly difficult to moderate it yourself.