To the best of my knowledge, 'normal' brick and mortar dispensaries dont stock things that potent. A 1000 mg edible in one go would be kind of the same thing as banging back half a bottle of Everclear because you were 'thirsty'.
Maybe its changed since ive been to a store but the website that I was looking at, that happens to service Cornwall has the little bricks that are meant to be split into portions, and I think those ones max out at like 100mg for the entire bar or something.
I find it difficult to believe that she was capable of consuming literal thousands of milligrams of thc a day (my god the monitary cost!!!), let alone functioning on doses that large.
Feel free to vote me autistic.