She may very well be bisexual, but this quote does not prove that.  A lot of conclusions can be reached about her quote, one of which is that she is, in fact, bisexual.  Until there is better evidence though, it would be imprudent for an encyclopedia to claim that she is definitively bisexual.  She could be bi-curious.  She could have just experimented in the past.  She could have been exaggerating.  The magazine could have been hyping her quote since it's marketed to lesbians.  One ambiguous quote just can't be taken as definitive, especially regarding sexuality.