Do all of your children have the same Dad? Are they relatively close in age?
My ex and I have 3 kids (16,14,11) and despise ex's gf (who was ow) trying to discredit me, they kept each other grounded as to what was going on iykwim.
Have you ever spoken to your dd about why you initiated the split? It depends on why you split but by age 14 she probably has experience of friendships drifting if growing apart is the reason for your split.
Do you over compensate for the split and be too positive about their Dad? My ex apparently compliments me a lot and the kids are 
because he wasn't like that pre-split. They find it fake and creepy. I only mention him if an anecdote involves him or I ask a question like what time he's picking them up.
Is her Dad in a new relationship? Like my point about drifting friendships, you can say it's good that her Dad is happy with X.
I'm not sure about taking her phone away. It's personally something that I struggle with when it comes to teen parenting. Maybe my expectations are too low but I've never gone longer than a few hours of device free time with them.
The knocking on the window thing seems weird. A normal parent would text teen and teen would go out once parent arrived.