If you are certain its not a stray (does it look healthy and well fed?) then there are a few things you can do...

Many cats have multiple homes, and it seems she's adopted you - unless you want to encourage and semi adopt her then you will need to do something to discourage the little visitor


There are things on the market to help discourage them coming into your garden - from pepper pellets to lion poo manure (good for the roses and no little cat will come near apparently)!

If she comes into the house or you want to move her on - use a water pistol, harmless but usually enough to deter an unwanted visitor.

Hope that helps