Yes tell her about the power now

When she returned, you were already sitting in her bed eating the pizza. She frowned, and then joined you in bed and grabbed a slice of the pizza.

“Hey, Jemma, I have something to show you, it’s a gift I was given” you said, leaning over to her.

“Oh yes? Do tell”

“You’re going to laugh and call me crazy, but I’m going to tell you anyway. I have the ability to change and alter anything in reality, simply by thinking about it.”

Jemma started to laugh, but for some reason it turned into a giggle. Her breast flesh wobbling and jiggling about the place within her bra. "You really think thats true?" she asked.

“Fine, put your hand out” you said. She calmed down and reached out her hand. You focused, willing for a sheet of paper to appear. She was watching her hand intensely, and let out a small yelp when a piece of paper suddenly appeared in it. “What the...” she whispered, turning the paper over, looking at it, and then writing on it. “Its true.”

“Course it is, you really think I’d lie to you?” you asked, pretending to look a bit hurt.

“No no no no, its just, wow. What are you going to do with this power? Why did you tell me?” she put the piece of paper gently down and adjusted her bra.

"Because together we can have quite a bit of fun with this power do you not think?" you responded.

"I like your way of thinking" Jemma responded, before kissing you again, and eating another slice of pizza. "How about, we finish this, you strip, we get some sleep and have fun with this power tomorrow?"

"You are always so mature in your plans" you joked, poking her breast flesh, causing her to moan ever so slightly.

"Shut up and eat" she joked.