With some conditions, yes.

"I'll accept your little game, but I have some rules I want to lay down first?"

"Oh? Go on, what sort of rules did you have in mind?" She looks amused by your words.

"First, I need proof that you'll actually follow with your punishment if I win the bet. I need something that can reassure me that you won't just run off or seal me in the mirror anyway afterwards. Second, you can't manipulate anyone into sleeping with you. They have to fully conscious of themselves and actually willing. That means you can't use ****, manipulate their minds, or use aphrodisiacs and whatnot."

"So far it all seems far. Now usually there's a third condition when you humans talk like this. So hurry up and tell me what your third and final rule is."

You smile. "The third and final rule is that you're not allowed to leave this castle during the bet."

"What?!" You feel some satisfaction that you've finally caught her by surprise. "You've got to be kidding me. You want me to stay rooted in this one location while you have the freedom to ride to any village as you please?"

You shrug. "It's a large castle. We get lots of visitors, and there are plenty of servants and guards around too. It's not like I can even go that far given that we only have seven days to complete the bet. I don't think this is too unreasonable."

She pauses to consider this for a moment. But in the end she shakes her head and growls, "No. If I must stay in this castle, then you must as well."

"Now you're being the unreasonable one. I sometimes need to run errands outside, and I can't exactly tell anyone that I can't do the errand because of a deal I made with a demon."

"... Then let's compromise. We must stay within the same location during the entire duration of the bet. If I am within the castle, then you must be as well. And if you want to leave, then I must accompany you."

"Hm..." You think about this, and the change doesn't seem all that bad. "Alright, I can agree with that. So you're fine with the other two conditions?"

"In spirit, yes. But to be honest I'm at a loss as to how to fulfill the first condition of yours. Obviously you will not take a verbal vow from me. I can use my powers to create a mark of our vows that will have dire consequences if we break them, but you don't seem like you have magical knowledge to be able to confirm that I'm actually casting the right spell for the purpose. Did you have any ideas on the sort of 'proof' you wanted from me?"