She takes advantage of the situation

Naomi couldn't stand that the master would pick Megumi over her. She worked so hard to appease him, she even went out and secretly ate some humans outside of the village to unlock her blood demon art. Fortunately her blood demon art was something she could use here. She called it Hypno-shine, she just needed a shiny object that can swing and she can hypnotize almost anyone. She took a shiny gold coin from one of the humans and tied it to a string to use as a tool and now was definitely the time to use it.

Naomi would come up behind Megumi, holding the coin between her and Tanjiro and beginning to swing it. She made sure to cover her eyes, as something she found out was that if she wasn't careful she could hypnotize herself too.

Megumi saw a shiny gold coin drop down in her vision, and as it began swinging, she couldn't look away. Something about it was so pretty... Like she just had to stare at it... As it swung back and forth... Back and forth... A sleepy smile started to grow on her face as she started to grow tired. It became really hard to think. She didn't need to think though... She just needed to stare... And Obey.

Naomi giggled mischievously as she stopped swinging the coin and saw the vacant blank stare on both of their faces. She'd wave her hand slowly between them, to no reaction. "Are you both really hypnotized?" She knew the answer was yes, but she wanted to hear them admit it, maybe it'd be funny. "Yes." was the simple answer that they both said, in monotone voices. "Good! From now you'll refer to me as Mistress, and now stand at attention!" She'd watch as the two would get out of there position, standing up and obeying her command "Yes, Mistress." They'd say, again in their monotone hypnotized voices.

Naomi's skin would shiver with such a pleasurable chill. She loved this, it made her feel... Powerful. Like master. Maybe she'd be able to be his second hand lady if she showed off her Blood Demon Art. Not using it on him of course, she'd never hurt her master. Maybe she'd show him how she's controlling Megumi and this boy. Her hand would slip down to her Kimono's obi to begin undoing it. She'd reach down further as her Kimono began to slip off her shoulders, slowly touching herself as she'd watched to two just vacantly stare forward while waiting at attention.