Re-haft it, and then show the "Girlfriend" how sharp it is, and then either sit her
down, and explain how fragile obsidian is, and the skill, and time it takes to make a blade like that, or get another Girlfriend, that is not so inclined to step on things.
I think I would have to tell her not to touch another thing in the house, and to sit down, and wait for a half hour, read a harlequin or something, while I go outside to cool down. Boy that is a sickening sight. Too bad, but poo poo happens, so just re-haft it, and go on. Just don't leave it out again.
Wayne