And very likely she intends to leave you to simmer till at least after Easter. And then maybe start making conditions with which you have to comply first. Perhaps related to other kinks she has.Ace. interesting she is dating, so likely she'll want to lock him too.
Re key, I'd say best she keep it for now as in real emergercy she can send code to lockbox.
And why shouldn't she?
Point is: it's all about power. She has it, so what's the point for her if she doesn't use it to her maximum advantage. And makes you do as you are told. I'd say she is natural Dominant and you are a natural submissive so you should be a good D/s partnership as she'll have you just where it matters and you will both know it.
So go with the flow!