Where is your computer located? Do you have a webcam? Some webcams have extra features where you can set it up as a motion detector. Just make sure you computer is left on and have your monitor off.

I know there are chemicals that you can put on the patio door handle, that when someone touches the chemicals, they turn colors and don’t wash off. You might try that. Or, you could try a bluff, and tell your neighbor that you do have a surveilance cammera and that she was caught on it ( the time that you were home.)