I'm a bit confused. Lots of people take large doses of B12, but it's generally measured in mcg, not mg. I'm not sure how she could take that much unless she was taking a whole lot of pills. There are people who have a deficiency who will be put on very large doses by their doctors. Most of these would have a genetic condition that affects the ability of the body to assimilate B12, and it would be in a methylated form. Are you sure she was taking that much or did you mean 1000mcg? As for how long it takes to leave the body, a lot of it will leave when she goes to the bathroom, but although it's considered a water soluble vitamin, as is folic acid, B12 does in fact store some in the liver. The rest will leave, again, every time she urinates, and generally, it's not considered toxic unless for reasons other than taking too much, in other words, in someone who has a problem with it chronically. I don't know what you mean by her having a "rosary" on her neck, do you mean rosacea, a symptom of B12 overdose? I assume she's seen a doctor, as she knows her blood level. What did the doctor say she should do? Did the doctor say there was any danger? There are ways to flush out the liver, but it won't flush out everything, usually just toxins and not everything that's stored in there. There are herbs that do this, such as milk thistle, but her liver isn't what's really in danger, and the B12 in the liver is stored to be used when needed, so since it isn't currently needed and most will be excreted in urine I don't see why this is a big problem. Time will fix it, unless her doctors have discovered a reason to believe otherwise.