How do I find Pem? I encountered her on Forest territory level 1 before I had the items I needed. Now that I have them, I've not seen her. (I'm currently on territory level 9) Any help with this? How do you find her and what is the scarf she'll give you?

Only way is to keep exploring.

I think she only appears during FMC as well

After some digging, I believe this is the case. She gives you a scarf using blue yarn, meteorite and star dust. There is a blue cosmic scarf gear which is the only scarf that makes sense. It can be bought in the FMC store, but I'm assuming this is another way to obtain that scarf. Also makes sense, because I started playing on the last or second to last day of FMC before knowing what it was. We'll see at that time I find her again :)