Whoa lots of responses overnight.
Yeah so if you want the details, what happened was my two friends Jeff and Rickard came over. Jeff has come over twice since I got Willow to watch movies, Rickard had only been inside for a few minutes to drop off a cookie tin and so she doesn't know him as well.
Rickard came first and tried to offer Willow his hand before I got a chance to tell him to ignore her, so she growled at him, full hackles, and I told Rickard to just ignore her and act like she wasn't there. He obliged. Jeff immediately came in and sat down without acknowledging Willow at all. Within a minute Willow came over to him, sniffed and let him pet her and wagged her tail because she knew him a bit better. Took her another minute of sniffing Rickard but then she let him pet her too. So really the "warming up" period is not that big a deal.
Problem is that then she just gets nervy and paces around and around the room like she doesn't know what to do. I'd put her in "place" near me, she'd sit for maybe 5 minutes but then get up and pace some more, going between Rickard and Jeff, not really sure what she's doing. Eventually she did settle down.
Problem was that Jeff (who's really loud, was laughing super loud and annoyingly at the movie--that's just how he is) went up to go to the bathroom and when he came back, he smacked Rickard hard on the arm with his beanie in a joking way. That really set Willow off. From her lying down position, she started barking pretty ferociously at him, like he'd really freaked her out (it didn't take place near her--she was lying beside me). I tried to tell Willow to stop but she barked probably 10 times and then was all huffy and wouldn't go near Jeff, and kept kinda mumbling at him. Jeff apologized and said maybe she had some PTSD from being hit or being in a family where people hit each other or something...him hitting Rickard with his hat was some kind of trigger.
After she calmed down I decided to put her in her crate, which is in the same room. She went in but sat pressed up against the door the rest of the night, watching Rickard and Jeff and grumbling now and then.
I've since put my spare crate in another room and will plan on putting her in there in future; out of the way, quiet, she won't be bothered by people. My dad is coming to stay for a few days--he's a large, large man who doesn't really like dogs, but he's going to have to sleep in the living room where Willow's crate is because he can't do stairs. So...I have options, we'll see how it goes. Maybe because he doesn't really like dogs it'll be fine because he'll ignore her.
So there's the whole story. Willow really warms up to strangers rather quickly, but then is SUPER reactive if they make a sudden move.