You can't make her do anything that she doesn't want to, and it's a waste of energy trying, to be honest.
If this isn't working for you, then you have to tell that to your boyfriend and not take the "it'll get better" answer when you know it won't.
If he won't listen, then you need to end the relationship with your boyfriend.
Please check out The Birdcage - an open, friendly Polyamory forum for all parts of New York State
"Listen, or your tongue will make you deaf." - Native American Proverb