My suggestion is to consider moving her away from the hot or sharp pointy objects so she stops hurting herself FIRST since this is your absolute obligation as her employer or supervisor. Then, after an appropriate (re)training period and review, if she doesn't measure up, I'd consider terminating her employment. I would also consult with a HR mgr or employment atty before making a final decision.
If you terminate her now knowing she's been injured at work you're opening a HUGE can of worms with almost limitless liability potential. Document, document, document EVERYTHING from a fair and unbiased standpoint that gives the employee more than enough chances to work for you in some position. Remember, from a business standpoint, spending 5-10 grand on wages, retraining employees, better job skills, and stuff like that is a LOT cheaper than spending 500 thou to 1 million in legal fees and judgements. Been here, done this and am richer because of it.
I find that most employers' documentation is insufficient and that their "reviews" are little more than complaint and humiliation sessions. Be fair. Be MORE THAN fair and have clear documentation that doesn't just point out her shortcomings in offensive language. And it needs to say more than "get with the program or you're fired".
Last, calling someone an "idiot" and asking how to fire them speaks loud and clear as to the type of issues she has to put up with at work. Not insulting anyone (even if it seems like it) with this statement. Just pointing out that most people believe that they are the best-of-the-best in the entire world. If that's the case then the rest of us make at least one mistake once in awhile. It's why WE aren't "the-best-of-the-best" and you are. So, give us a break and find out why we made the mistake so we won't do it anymore BEFORE you rag on us about it. Remember, we're clueless and you're perfect. Help us out a bit, eh?