Thanks for the replies idiots!
She only does this once a month, sometimes less. She go's out with her friends for tea then a club and comes home about 3am.
If she's gone I can't leave the house as I'm looking after the little one.
As I said I know she's not doing anything but I still have a problem with it when I know I shouldn't.
I leave her all the time lol sometimes I stat out all night!