Without reiterating what everyone else has said, I think she is actually just jealous although she might not act it, but she may be scared of losing you as well. But you've been friends so long, your boyfriend isn't worth ending your 17 year friendship with. The best solution for all would be a way to make all three of you happy her, you and the boyfriend. Are you spending enough time with your friend? If you're not perhaps she feels "replaced".

Here is a quote I recall from someone, I think it's true...

"Girlfriends/boyfriends may come and go but best friends are there for life"

Edit

Eh late response, but still ...