This is just MY personal thoughts. I was addicted to crack. If I were to be driving someone's vehicle and found a crack pipe, I would throw it out the window going down the interstate (I did, only it was my car but someone else had left the crack pipe when I relapsed and I found it 2 months later). I would not pick it up, put it in my pocket, meaning to throw it away.
If she's using, it will become obvious. The main issue, right now, is are you comfortable not trusting her? What are you going to to do if she IS using? Please focus on YOU and keeping YOUR peace and serenity.
Hugs and prayers!
Amy