[xela]

My daughter (youngest of 2, older one is 15) seems to be having difficulty sleeping alone at night. She was fine for years, and this has surfaced following a couple of sleepovers when she called us in the middle of the night to say that she couldn't sleep, she was feeling sick, and could we come and collect her....
Since then, she's been unable to go on sleep-overs - she's tried, but the same pattern follows - feeling "unwell" and wanting to go home e.g. 2am
Now it's taking a new pattern - some nights (many nights) she can't go to sleep, going to bed at 10pm but coming through to us at midnight wide awake, unable to sleep and worried that she'll be tired the next day. Myself and my wife let her sleep beside us, and she's just fine.
This seems to go back to a time when we met a family who's mother had just died of cancer. She seemed to be deeply affected by this and the problem with sleepovers started soon after. This was 18 months ago. The recent aggravation started with my thoughtless sister spilling the beans about the fact that we've privately organised for her to be cared for by a particular family in the unlikely event that both of her parents die.
She talks about a "worry bug" that gets into her head, and we've discussed ways of getting rid of it, like thinking pleasant thoughts, counting sheep etc.
It's not a huge problem, but we don't know what to do about it. How seriously should we take this? Will it pass in time? Should we go and talk to someone professional about it? Part of me feels that by making an issue of it, we could even worsen it.
All thoughts would be appreciated.