You think for a second. Then, you ask her to lift the couch. She does it with ease, holding it aloft above her head with straight arms. Then, you grab everything heavy you can find; your weights, tables, chairs, and even the TV. With each added weight, you watch the amulet glow and her arms surge bigger every second. But that's not what you care about at the moment. When you've created the heaviest, most precariously balanced mountain of items, you give her an order. "Now drop it on your head."
Lisa pauses. "Hold on, that doesn't seem..."
"Are you scared, Lisa? I said drop it on your head!"
Goaded, she sneers at you before dropping the entire load, which would weigh over 2 tons, down onto her head.
It flattens immediately. There's no gap between the sofa and the floor. Her head has been crushed to the thickness of paper.
You laugh. "Ha! See! I was right! Your skin might be tough, but your bones aren't! I win!" Then it sinks in. You just crushed your girlfriend's head. You just killed your girlfriend! You start to hyperventilate. What the hell do you do now? You're a murderer! You're going to get sent to prison and spend the rest of your days mourning and-
The amulet is shining brighter than it ever has.
Slowly, but surely, the couch and all the things piled on top of it begin to rise. You watch in horror and amazement as Lisa's head uncrushes itself, popping back into shape, before slowly lifting off the ground. Her neck muscles surge with growth, growing longer and thicker as she lifts two and a half tons of weight with nothing but her neck. She tossed it aside, laughing as she stands before you.
Her body, swollen beyond the realms of possibility, is 9 feet alone from foot to shoulder. Her shoulders roll back as she cracks her knuckles, bones now denser than steel, and body unable to die from the sheer speed of her healing factor.
Then, sitting atop this monstrosity of pure, inhuman muscle, sits a thick appendage. Three feet long itself, her neck is thicker than your entire torso. It moves around atop her body like a snake, a prehensile limb she never knew she could have. And on top of it is her large head.
Her entire face is muscle, but it doesn't detract from her features. In fact, Lisa seems to be even more beautiful than ever, with the newfound musculature lending her features a more defined and chiseled look. Unbeknownst to you, the new muscles allowed her to manage every microexpression she has, making her a perfect liar, and able to manipulate people's emotions with ease. Not to mention her cheek alone could bounce twice your body weight with a flex.
Her eyebrows arch into a playful smirk, with a hint of arrogance. You can't help but feel grateful for your loss, brought before such a powerful creature as your girlfriend has become. You can't call her human anymore, and she certainly doesn't consider herself to be. Her neck entwines with yours, and gently she lifts you off the ground with her snake-like appendage alone.
She constricts her neck, bringing her face to yours before her lips crash against you. They're far larger than yours, and you can feel the sheer power in such a small organ as they expertly suck and force your mouth open for her entry. Her tongue darts in and flicks around your mouth, quick as a serpent's strike. Even that is pure muscle, and as it pushes its way through, it snaps one of your teeth clean in half. You barely notice it, however, as her arms come up to fondle your tiny body, a hug made entirely from the 12-foot giant's hands.
Lisa suddenly pulls away, leaving you gasping for breath at the absence of her touch. You fall to your knees before her. She gives you a grin. "You're such a clever little boyfriend, thinking up ways to make me stronger," she says. Her finger, which is meaty and thick as your wrist, comes up to stroke your cheek. You tremble at the touch and bow deeper. "I had to reward such good behavior. But, unfortunately, you did lose against me again, didn't you?"
You look up at her again. Something strange falls over you the more you look at her expression, something innate that makes you feel so vastly inferior and subservient to the goddess before you. "...Yes, I lost to you," you admit quietly.
"What was that?"
"I said, I lost to you."
She cranes her 3-foot neck closer and holds up a hand to her ear. "Ah ah, I can't hear you!"
"I said, I lost to you!" you cry, and bow until your forehead touches the floor. "How could I ever compete with a goddess like you?"
You feel a hand gently stroke your hair, but with enough pressure to keep your head firmly down. You don't deserve to look upon the goddess without her permission. "Goddess..." she muses. "I like that name."
Lisa lifts your head up, taking your entire body with it as she dangles your limp body with one massive hand. She studies your face closely. "Yes, I think it suits me well. And, you shall be my pet, won't you?"
You nod.
She smiles gracefully. "Yes, you will be a good pet. And such a smart pet too. I'll tell you what, you can help me improve my body even more. And you can start on whichever part you wish."