Narssist Roomate: Coping advise

Hello, Thank you for taking the time to read this. Anyone out there have experience with a closet narcissist? ;) So usually I can avoid her. My girl friend and I lived with her for almost six years - I want to move out in 2 or less btw, but we aren’t finically able atm. Usually, my girl friend is a rock, water on a duck- all her shit she throws doesn’t even effect her(at least outwardly.) Unfortunately, our roommate has always acted like an older friend, someone to talk to, like a Sister.. which is why it hurts so bad when she ‘jokes’ about my girl friend to me, says hurtful little things or low jabs- I try to ignore her. She cheated us 40 dollars rent - I chalked it up in my mind that she’s treated us out before, and helped with food in the past, etc, I’ll over look it. This past weekend though, she REALLY hurt me, acted crazy abs bizarre. Here is what happened: It’s stupid and petty, but this is poison and I need help dealing with it. I had a plant that needed transplanted and she is good with plants. She agreed to transplant my plant. She handed me the plant back in the bigger pot, and when I grabbed another for the smaller pot that is just emptied, she ga e it back - in a different random pot she had given me that she got for free. I took it bewildered. How did she use that one? Why would she do that? I asked her, not wanting to outright accuse her, ‘was this the pot it had been in?’ She looked me in the eye and said yes. So, she has lied before, flipped out and got snappy and stupid shit but generally respects our stuff. This felt like a huge power play. I was so hurt and angry and baffled - why would she have done that? Why would she take it? Had she asked, she could have had it. Had I imagined it? I was seriously reeling. Everything in my body wanted to confront her but what good would it do? She would have denied it again, hurting me again/ making me look like I was the hysterical one or accusing her. I felt so crazy, like did I actually give her that one? I had kept replaying the morning bc it was so bizarre. She kept acting like everything was fine. I told myself I would ignore it and look for it later - I would take it back - that would show her. But she hid it. She was on the patio, where could it have gone? She took her dogs out a few hours later - returned with something from her trunk - a gift from work that she wanted me to have, as though she knew I was mad and wanted to show me what a good friend she was. I feel poisoned. I want to confront her and say “I’m not stupid. You didn’t fool me, btw. Why did you do that?” She always says you choose your family, and lets us believe she is our friend etc. But she will plow over the conversation, always back to her, roll her eyes, slowly push our things out of the shared space(living room,) and I’ve put up with it... but I feel really scared living with someone who is that much of a power freak, a psycho who can look you in the face and lie. It’s so stupid. I am ashamed and angry that I just pretended to be fooled and ignorant. Do I say something or just keep this in my mind and get another reason to not trust her? Thanks for listening.