here's a question, can I change the locks on my house?
I would first ask politely for her key. It is more of a symbolic physcological gesture. To her, it would mean that she is no longer allowed to come and go as she pleases. From her latest demeanor that you describe, it does not sound like she would be hostile.
You need to think long and hard of what to say so as to make her understand that you are not comfortable with the way she can come and go. You also need to discuss some sort of sharing of time with D13/D17 so that your W's time with them is not on your turf.
And there are some bonuses...when your daughters are spending time away with W, you are free to invite some of them Red Bull girls over
