Monstrous power.

Ten thousand scents and sounds, each more potent than the last, assaulted Karyn's senses. She waded through them as best she could, mentally sorting the scent of a frightened squirrel from the chirp of a nesting sparrow.
The fur on her calves continued to thicken as she walked, shining with beautiful luster. Karyn stopped in front of a parked black Corvette to look at her bestial cast in the tinted glass. She gasped in astonishment at how deeply she had changed. Wait until Jon sees this!
Her billowing hair was now thicker than before, and spread into a definite mane. She could see the tips of her ears through a break in the strands, pointed and tipped with the same fur that covered her flesh. They twitched and extended even as she watched, becoming more like an animal's ears. She sniffled with a sensitive black nose. Her facial hair hung down below her jaw, bringing images to her mind of the guitarists from ZZ Top. She chuckled gruffly at the thought, displaying sharp canine teeth. The lower pair were already more pronounced, looking like the beginnings of tusks.
"This is so wonderful," Karyn mused, posing in the small window. "I wish I knew what I'm turning into, though."
She gathered up her purse and was about to move on, when she felt something moving beneath her clothes. Make that several things. She grimaced, more like a snarl, and tugged at her clothing. Her claws tore through the fabric as the sensations intensified. She felt like her muscles were being yanked through her skin, yet there was no pain in the writhing motions.
Through it all, Karyn remembered the trip to the Rockies with her father. She recalled the avalanche, being separated from her dad, and the creature that freed her from her snowy crypt. Her true memories of her father, of the divorce and years of neglect, faded blissfully into the ether.
She snarled and pounded the hood of the Corvette, leaving deep dents in the hood as its blaring car alarm triggered itself. Her skin was being pulled now, stretching and expanding along with her muscles. Karyn roared as she finally relieved herself of her clothing, freeing her body to multiply in height and mass.
"Hey!" A young man with bowl-cut blonde hair nervously approached the she-beast. "W-what're ya doin' to m-my c-car?"
The creature kept her warm, fed her, and thus claimed her. It adopted her as its own, to raise her in lieu of her human parent who had not survived.
Raw power flooded her muscles, and she gripped the hood of the Corvette, puncturing completely through to the frame. The drone of its klaxons hurt her ears, and she focused her strength into the offending machine. Karyn deadlifted the car with little effort, military pressing it over her head. She bellowed like an untamed monster, her thoughts dulling as her instincts rose to the surface. Bystanders screamed and scattered, terrified of the massive nine-foot beast-girl.
She was not human anymore. Soon, she would take on her true form.
The car's owner stumbled over the air behind him, and scrambled away for dear life.
Sasquatch.
The word struck Karyn deep in her mind, and she shook her head in confusion. Her muscular arms kept the Corvette aloft, and she gasped in amazement at the feat of strength. Karyn set it down as gently as possible before retrieving her purse and backing away slowly.
Once clear of the scene, panic drove her to a destination. She ran, grunting but not tiring.
I've got to find Jon, she thought. He's the only one that can help.
She remembered her purse, and yanked it open to retrieve the stone.