Are you Scared of letting cat out for the first time? Why not train you cat to come running when you shake the biscuit box?
Also, don't feed her before she goes out and she will come back when she is hungry.
Try not to worry, cats know where their home is :)<

Electronic cat scarers send out a high pitch sound that cats don't like.
They come as battery operated or mains powered. The battery ones activate when cats pass by them up to a hundred metres and the mains one works continually. They are available from garden centres.