Cat burglar?

Princess aka Ellie is our next door neighbours' cat. She is a 2 year old Burmese Blue who has been re-homed with them a couple of months ago. She is a lovely friendly cat BUT she seems to like our garden more than her own and it is really upsetting our two cats. Here she is trying to get in the front door. So I pick her up and carry her round to her own garden. I must watch all this as I could spend a lot of time go to and fro!