Probably best to confront her first.

"Louisa! Hey, Louisa! Wake up!" you say sternly, shaking her.

Her eyes slowly open and she groggily moans. She rubs her eyes and looks at you. "Max? What are you doing here?" she says, clearly hiding something.

You pick up the book to your left and flip through it. "What is this?!"

Louisa grates her teeth and hops up quickly. "Listen Max, I got it at some weird yard sale. The vendor was some creepy old dude who I thought was lying. But that book is powerful. I..."

She then realized why you were probably asking about a random book in her house at 10 in the morning.

"You... weren't aware for that, right?" she said, unnerved.

"I wasn't aware, bruh. Of course I was aware! I was **** to watch as you jerked one out in my body! At least have some restraint or the common courtesy to clean up after!"

She blushes and sits down. "I'm Sorry Max, but it felt AMAZING. It literally felt like a volcano explosion. I couldn't help myself!"

You harrumphed and sat down. You were less angry now and more curious.

You look at Louisa. "What do we do now?"

Louisa looks around. "It was fun, wasn't it?"

You couldn't lie. It felt good, and you told her.

"Then why don't you possess me, or I can possess you again and have more fun? Or we can just possess someone else entirely?"

You look at the book, feeling some kind of evil energy coming from it.