I would say go with straight visualization, or a petition. It’s the least risky in terms of attracting unwanted spirits that you can get if you try evocation without setting up protections first.
It’s still a good idea to cleanse your space before your start though.
Simple space cleanse:
Simple shield you can put on you and get your gf to do the same:
How to do a petition:
How to use visualization: (do this during the petition anyway if you use a petition - this version also shows you how to use it for making a kind of ward/shield)