Sounds to me like she thinks you're a limo and the cost is to con you into giving everyone a ride. Technically, food is a drug too. Anything that enters the body that has a chemical affect on the body is a drug (or something like that). What you should do is reverse it on her. Next time she's saying that you were high, be like, "No, it wasn't me, it was you." Then when she denies it, be like, "You just don't remember because the drugs make you forget." After a few times, I'm sure she'll get the hint. Either that, or she'll get real pissed and then you can tell her that it pisses you off when she makes comments like that to you (or about you). No offense, but if it were me, I would have shunned her a long time ago, or more likely, would have really chewed her ass out to let her know that her shit won't be tolerated.