I've had many good nights dating bisexual women so it really up to you and how well you deal with jealousy and your own emotions. I say stay with the person. It could be great or you may just break up anyway but you never know til you try.
love is love i think that is the most hardest thing in the world, along with love there is unconditional love, that means you just deal with it, but no matter what anyone says love usually wins, then you have to ask yourself are you willing to share? usually no.. then there is the fact he or she has been this way a long time. even if they say ill change or let go it usually never happens. so if you want a long a painful road ..stay. when you get sick and tired then maybe you will see more clearly..