...Followed her to her friends house (she never told me she was going there). Then to another house, and then be popping around the neighborhood.
.... So, what is the limit. When does it become "spying".
...What do you think?
You may want to go through all of her personal items in her bedroom and look for any loose floorboards, secret cubby holes in her closet. Just to be sure she isn't the local community drug dealer or mule. *Kidding* Anyhow, you already answered your own question. It's spying when you follow and track. Occasional cars and dog walkers as you pan camera, that's sightseeing. Focusing on a dog walker for longer than a glance, zooming in to catch him/her reaching behind to pull a handful of buttmunch out of their crack and recording it on video, that's spying. Common sense stuff.
Pretty sure your locality has a published rule that dictates the minimum altitude for flying a drone, and which specifically emphasizes residential areas and reasonable right to privacy. Here in Vegas, the minimum is 275 feet. Ceiling as we all know everywhere is 400. Reasonable Right To Privacy, and in conjunction with locality and FAA rules and plain common sense should already define certain and acceptable behaviors for an R/C pilot. In your case, you let your entitlement and curiosity as a parent to a child, override the first and foremost intent/goal of owning and piloting a drone, which is just simple enjoyment and recreation of flight. If you have to wonder about your kid while flying a drone, you're greatly missing the point. ...I'm sorry if that sounds preachy and lecturous. lol. Not trying to be. The alternative to what I've already spewed, was, KISS. Keep It Simple Stupid. Enjoy your **** flight brother. Tracking/Spying and wondering implies way too many, extraneous, thoughts on your mind, distracting from your focus piloting an R/C aircraft. But, *I GET IT*, perhaps you saw this an opportunity to practice a different non-boring piloting skill which is, quite frankly, tracking. A tremendous word.
Personally, I'd practice on more exciting objects, such as anyone with an ATV out in a remote area kicking up some dirt, group of cyclists charging down an open remote road (with their permission), moving train at the outskirts of town, stuff like that, that results in some great video footage. Daughter zipping around the hood? Well, if you're just in the habit of discharging your batteries for no practical purpose then, you probably did great. Did you zoom in on her scalp to see if she's flaking and shedding? hehe.