It may not have anything to do with jealousy. I am not comfortable with overnights, for myself or Karma. I feel as husband and wife, our place at night is in bed together. I don't care how late he stays out, but when it comes to bed time, we're together. This isn't set in stone, if someone were to enter our lives to point that they truly were a part of our family, I may feel differently. I usualy had no problem when he stayed the night with our wife and I was home alone. It was because she was family.
I think you just need to give her time. If she says it's because she doesn't know you well enough, that may really be it.
It may be other stuff as well. But I know personaly, it bothers me when people read to far in to what I've said. I am a very literal person, if I said it, that's what I mean, not whatever you think is in between the lines. I don't write in between lines.
Now maybe she does, I dunno, I don't know any of you. But I just wanted to share something from the other side.
If you're right, and she just hasn't faced some things, give her time. Ask what she needs. And don't assume you know what is best for her, or how she should handle things. Not saying you are, don't take it that way, more of a don't let it start going that way in your frustration.
Cricket and I had a lot of issues because we assumed we knew how the other was feeling and why. Instead of talking and asking questions, we both went on with our assumptions and put Karma in the middle. Try to keep lines of communication with her open on your end.