If she told you where she was going, might that be a bit of an open door? Will Karen help you keep in contact with your daughter at least? At least she didn't just disappear without leaving any trail.

Has she had a history of depression? Or anything that might explain this?

I am really sorry this is happening to you. Not knowing why is a hell in itself.

I am glad you have friends that are coming over and staying with you. That gives added hope. If you are someone that people care that much about then you must have something of value you are giving to others.
shine that light of yours!
Love,
Teresa