Were you going out with her four nights a week before you moved in with your boyfriend? Unless you are suddenly working 50 hours a week to support him (unwise) I highly doubt it.
As you rightly said, it is insane jealousy, combined, I would guess, with a lack of confidence on her part. You have a full and busy life and a (semi)permanent partner now. What does she have? You are leaving her behind.
She really doesn't like that, especially if she was, for want of a better phrase, the dominant friend. The one who decided where you were going of a night and what your were doing.
My instinct is to tell her "tough." If she can't be happy for you and accept you now have other priorities, like sleeping and learning to live with a stranger, how much of a BFF is she? Then again, that is just me.
Talk to her. One on one. Let her know she is really bumming you out with this. The ball is then in her court.
Good call, MM.
If part of the issue is that she truly was the dominant one in your friendship, that shift could very well be at the crux of the issues you're having. My best friend from High School and I had to go through that transition as we grew up and matured. She was definitely the one in control and, come to think of it, the first time we butted heads like that was over a guy!!
If this is the case with you, tell her. In my case, it was awkward for a while, but it really strengthened our friendship.
Yup, you have to tell her (well I don't know that you should outright TELL her) to learn to deal with it. I had a friend like this and as soon as I got serious with my boyfriend, she would CONSTANTLY complain that we don't hang out as much anymore, that I'm putting him over her, bla bla bla. Well, yeah, you know what!? We DIDN'T hang out as much anymore and I DO put him - my lover - over her - my bitter annoying friend. And she wasn't bitter and annoying to start, she became that way because of her own issues with how I live my life. We haven't spoken in 3 years now.. because of this.. so if you really want to avoid that future she has to get over it. And maybe you have to tell her that... though I can't think of a kind way to say it.
Usually I'd be the LAST person to say this, but maybe check out how you are treating her in the long run. Do you see her constantly, talk all the time and then suddenly disappear once you have a boyfriend, only to re-emerge months later after a break up demanding attention, a shoulder to cry on and constant invites to girls nights?
If you really are just overloaded, she'll have to deal with it, but do consider what you've expected of HER in the past