Hey! What exactly do you use to check that information? Saying that she is "100%" makes me think you're reading some kind of statistic. Which in that case, that sounds normal, as a Sim who likes both males and females at 100% qualifies as Bi. This changes her preferences in Attractiveness as well.
There are two separate values, one for preference towards men and one for preference towards women. When both are maxed out, that is recognized as Bi.