She was probably 70. In a supermarket, buying groceries. She positively REEKED of the weed. And the cashier had a terrible time with her: very confused. Had a hard time understanding how wallets worked. Hard time understanding how to put change in her pocket. A few minutes later, I saw her in the parking lot. I'm pretty sure she couldn't find her car.
I made sure I exited the lot quickly, before she put herself on the road.
I am dealing with an Alzheimer's patient who is exactly like that. What you describe are symptoms of dementia, not marijuana use.
How does she act when she is not smoking?