@Jillian136 This doesn't sound scammy to me, but like a young person who obviously doesn't know how Airbnb works (her questions about why she'd get charged right away when a host accepts, if she has to pay all up front), but is consciencious about making sure she knows everything about what she's booking, which is a good sign. It could indicate that she'd be high maintenance but not necessarily. I've had guests ask a number of questions, depending on what their needs and concerns are (single females will often ask if the 20 minute walk into town and the beach is safe).
Someone would have to be a pretty sophisticated scammer to come up with that list of questions about the animals, the parking, if coming home late would disturb you. From what I've read from other hosts, someone planning to throw a party or commit theft just misrepresents their intentions by saying they are having a small gathering with family to celebrate a birthday, are coming to visit their mother, that sort of thing. What I can't imagine a scammer doing is asking you questions that show a lot of respect, like her asking about disturbing you, volunteering the info that she's never actually met this guy, being understanding about you maybe not wanting to host 19 year olds, etc. But even the most cautious and savvy people, hosts or not, aren't immune from being bamboozled.
And it can work the other way, too. The booking I was most wary about turned out to be one of my all time best guests, which is saying a lot, because I've luckily never had a stinker guest, they'll almost all been awesome.
The only thing that would concern me about this booking is, as others have mentioned, that she actually doesn't know this guy except for online communication, or phone calls and texts. And she is quite young, so could be very naive- for all she knows, this could be some 60 year old predator who posted photos of a cute 19 year old guy. But maybe she's as cautious as her questions about your listing indicate she is, and has checked him out thoroughly through reputable channels. There's really no way of knowing.
If you do keep this reservation, I'd be really clear about expectations. Such as cleaning up after themselves when they leave, not going out and leaving all the lights blazing and the AC or heat on high, etc. Partly because they're young, and partly because they're new to Airbnb. People of any age can leave a mess behind them and be clueless or unconcerned about your utility bills, but more common among the young, I think.