Yes, wear a chastity belt.

"I want you to wear a chastity belt."

Carries hand subconsciously goes down to her exposed vagina, but you quickly grab her hand and pull it away.
"Theres no need for your pussy now anyway, right?"

"R-right", Cassie resonds, blushing at the blundness in which you speak to her.

Satisfied you continue, "Right. So I want you to wear the belt while I hold the only keys...and maybe we give Emilia a key as backup, what do you say?"

"Sounds good", Carries voice quivers a bit, but she nods reassuring, "That seems fair."

"And lastly", you put your hand on her chin and lift it up so she faces you. "Always remember that I love you"

Your girlfriend smiles. "I love you too"