Laying on the ground in a pool of blood is a grotesque mass of twitching, twisted limbs and bleeding, cancerous growths. She writhes, hissing in agony as, with a cry of anguished frustration, she uses her magic to slice off the swollen sack of bone and flesh that used to be her arm, a frothing pinkish water forming a new arm from the stump.
It doesn't have cancerous growths but it materializes badly deformed.
She screams in frustration and agony and switches to one of her legs, severing the mass of twisted growth before generating a new limb.
Her mind isn't merely impaired, it keeps actively twisting, making her do the wrong thing, but she is getting better at compensating for it with every attempt, and what else can she do, not try to heal herself? She's not going to stop just because her failed attempts have her suffering torturous amounts of pain; she can't risk replacing her ruined torso until she can get a limb to come out right.
She is already surrounded by a half-dozen grisly left-overs of previous attempts, a pile of carnage that quickly grows as blood spurts out of her almost as fast as she can conjure/transmute it.