I would just let it ride. Compress the crap out of it with a transparent compressor, lower it in the mix (it was too loud, which made it really sound worse than it needed to), throw some ambience on it and give it to them.
There really isn't anything that could fix that performance. Autotune will only fix the pitch. The timing, dynamics and delivery will still suck.
It shouldn't fall on you to tell her she sucks, if she figures it out on her own and asks for help, help her all you can.