Sounds like you have a problem. The fingerprints and the residue aside, your "Fiance" is blackmailing you and stealing from you.
Tell you what. Kick her out of the trailer. Search said trailer for missing pipe. If you do not find the pipe, your free and clear. Just don't let her back in.
I read your post, got tired of thinking, came to a conclusion, would explain that conclusion, but I'm afraid your head would explode. Besides, I am a stark raving mad naked lunatic who burns then pillages and could care less if you think you are better than me.