Slowly

Natalie knew that any sudden changes in her sister's behavior would cause Margaret to be suspicious, freaked out, and running for the nearest therapist, so she decided to start slowly. She only added a half dose of the aphrodisiac. In addition, while Margaret was showering, she sneaked into Margaret's room where her anal-retentive sister had not only laid out her outfit for the day but her underwear.

Natalie sighed as she looked at her sister's boring blue wool skirt, white blouse, and blue wool blazer along with her boring light blue cotton panties and white bra. Natalie had picked up a packet of itching powder at a local comic book, novelty store, and added just a small bit of it to the crotch and bra cups of her sister's underwear, just enough to cause a slight itch.

Natalie smiled as she skipped out of her sister's room. She got online and ordered a vibrator, batteries for it, and a dildo and had them sent to Margaret's office at the university. They would arrive it a couple of days. Today was Monday, and the items were scheduled to be delivered Wednesday. Natalie's plan was to have her sister become more aroused with each passing day.

Margaret finished her shower, dried off and dressed. She grabbed her drink, and drove herself and her sister to the university as Natalie had signed up for a couple of classes at Margaret's insistence.

Natalie noticed Margaret squirm a bit in her seat. "You OK, sis?"

"Yeah, it's just... nothing."

"You just need to get laid."

"Natalie!"

"What, you need sex! Sex! Sex, sex, sex sex...."

"Enough!" said Margaret. Sipping her drink.

"Sex!"

"Stop it!"

Natalie smiled. "Fine, for the rest of the day don't think about sex, but we both know you need to get laid."

Margaret groaned.

"Don't think about sex," said Natalie, knowing that if you told someone not to think of something, she would think about it more.

They pulled up into the faculty parking lot, and Margaret got out, slightly adjusting her bra cups without making a scene.

Natalie smiled as she watched her sister walk towards her building, stopping to take a sip of her drink every once in a while.