Contemplating murder

Mandy clutched the knife more tightly in her right hand. She moved close to The Other Mandy and looked at her threateningly. The Other Mandy just stared as fiercely back, as if daring Mandy to do her worst.
Mandy bit her lip and thought. Why wasn’t The Other Mandy scared? Didn’t she see the knife she held? Mandy was sure she would have been terrified if The Other Mandy had held a knife to her. But she would bluff. Then it clicked. The Other Mandy was bluffing. Mandy smiled.
She wasn’t sure why she wanted to kill The Other Mandy, but she was sure that it was the right thing to do. How could there be two Mandys in the same place? It didn’t make sense. There was only one thing to do. The Other Mandy had to go.
She raised the knife and made as if to strike The Other Mandy, who immediately let loose a high pitched scream.
“Shut up!” Mandy hissed. The Other Mandy was immediately quiet.
“Take it easy,” she coaxed. “It’s going to be quick and just the tiniest bit painful.” She was enjoying watching the various expressions of terror dancing over The Other Mandy’s visage.
Mandy stopped grinning, and moved up close until their noses touched. The Other Mandy was quietly begging Mandy not to kill her. Mandy thought about it.
“No,” she told The Other Mandy quietly at first, and then more loudly, psyching herself up until she finally said,
“No! You have to die.”
The Other Mandy saw that Mandy was faltering. The Other Mandy seized the advantage, softly at first.
“Please let me leave, I’ll go far away and you’ll never have to see me again.”
“Shut up!” Mandy was the one screaming now. “One more word out of you and I swear I’ll make it extremely painful.” Mandy was more mad at herself than anything else. She’d set her mind on killing The Other Mandy, and here she was losing both her nerve and her temper.
“You’re not going to do it,” The Other Mandy said quietly, but matter-of-factly.
“You’re about to make me,” Mandy spat back.
“You’re not going to kill me,” The Other Mandy was in the ascendancy now.
Mandy steeled herself and raised the knife, ready to do this once and for all.
“Mandy!”
Mandy lowered the knife again.
“Mandy, are you alright?”
“Yes mum,” she sighed.
“Could you come downstairs please?”
“Coming mum”
“Told you so,” The Other Mandy taunted.
Mandy snarled and walked away, turning her back on the mirror.