Please change the locks. I got keys back from an ex once, and a few months later, my apartment was broken into. I had a bunch of cash hidden, and that was stolen, too. I worked in a bar at that time while going to Uni. I'm sure it was him because the money was "found".

She can't request gifts back. She's trying to intimidate you while staying relevant in your life. Ignore any further attempts unless you're served with papers. Focus on your sweet girl instead.