"It doesn't take two people. I'm happy here thanks"

Plan ruined. What now?

Seriously... I don't think you've thought this through properly. That's an awful pretence to get her upstairs, you'd be better off inviting her up to see your awesome collection of rocks.

Or alternatively, you could just get intimate with her as you escalate touching while still downstairs (like most would) and drag her upstairs as you turn the heat up.