The bones flew towards her very quickly but she dodged them expertly. Sans growled and threw more at her. She dodged most of them as well, but one scraped the side of her face. This did not discourage her though. She wiped the blood off of her cheek with her sleeve and gave Sans the most determined look she could muster.

She spared him. 

He threw more bones at her, growling every time she dodged. Papyrus was howling with maniacal laughter as another bone scraped her leg and a second bone pierced the skin on her right ear taking a chunk off of the top. She whimpered in pain.

She spared him again.

This time Sans aimed Gaster Blasters at her. She managed to roll out of the way right before they vaporized her. The blast left a gaping hole in the floor leading down to the basement but neither of the brothers seemed to care. They were more focused on her.

 She spared him once again. "Sans please, I don't want to fight you," she pleaded.

"Oh, you think you can trick me that easy? Nice try kid." 

Spare.

"Nice try sweetheart." 

With the wave of his hand, a blue bone was thrown at her, lodging itself in her chest, directly through her heart. She stopped moving knowing that if she moved it would rip through her heart, flesh, and bone. She was trapped now. What more could she do? Trying not to move her torso, she looked around at the weapons surrounding her. Her eyes met Sans's one glowing eye. 

Her friend, her best friend was about to kill her. She knew that this was not the one she knew before. He was not the one she had befriended as she attempted to save the monsters and return them to the surface. He was not the Sans who had treated her to lunch at Grillby's or sold her hot dogs on her adventure. Not the one who passed judgement on her before she fought King Asgore.  And he was definitely not the Sans who she lived with. No, this was not the one who saved her many times, who watched over her, who protected her, but the dark, evil, other Sans whom she had never met before. 

"Sans!" There was authority in her voice now. Perhaps, if begging didn't work, force might.  "I do not want to fight you! What gives you the right to kill me? I made a mistake and walked into your house! I never hurt you, I didn't fight back! I am sparing you!" 

It hurt her to yell at someone. She didn't enjoy hurting anyone physically or verbally but her life was on the line now, and to her surprise, this tactic seemed to be working. The blue bone in her chest seemed to fade away and she could finally take a breath. The bones surrounding her dropped to the floor and faded away. Sans began howling with laughter.

Papyrus, however, was getting mad again. "Brother finish her! What are you doing?"

"Eh? Come on Paps! This human's hilarious! Not like the other ones we've had around here." 

"That's just like you. Slacking off and making excuses even when you had the kill in sight. You are a lazy, arrogant, idiotic, self-centered,  waste of space! I'll do it myself!" 

Papyrus threw bones at her without hesitation. She put her hands in front of her in a feeble attempt to save herself but nothing hit her. Not even a scratch. She looked up to see the backside of an evil, red tinted Gaster Blaster shielding her from the bones. 

"Oh, so I'm a waste 'ah space eh? Self-centered eh? Lazy? I'll give ya that one," he smirked, "but I sure as hell ain't an idiotic, waste of space." 

He snapped his finger and the Gaster Blaster in front of her fired its red magic at Papyrus. Papyrus dodged it with great skill and summoned his own magical attacks.

Though it was pure chaos in the house, nothing was directed towards Frisk. Nothing even came close to hitting her. She wanted to run out while the two were fighting and normally she would suppress the urge to run in a bad situation but she saw no way that she could help these two, so she gave in.

She made her way carefully to the front door, opening it as quietly as she could but she couldn't control herself as she turned back around to look at the brothers. Sans met her gaze while a Gaster Blaster blocked an attack from Papyrus. He raised his hand, grabbing onto her soul again and threw her out of the house. The door slammed shut behind her.