I wouldn't be interacting with anyone, and that feels wrong.
It wouldn't be without interaction: if she tries to stalk them, that opens the doorway for someone to noticing her, perhaps leading Lark to escape or use it as a distraction. Everything you do opens paths for other Roleplayers. Unless she's isolated totally, and she wouldn't be, others can reply.
I wasn't interacting with anyone when I had Shertul flip the fuck out in Wellborough, but it lead to Sophia saving him which led to everything happening at the gates. Just have your character do something, anything, and it is a gateway.
And Sanachan wasn't interacting with anyone when she had her elves bicker about maps, but that lead to them meeting Windleaf. They interacted with no other players, basically RP'd totally on his/her own, but it was a gateway.
One example: If she stalks, others might notice her, leading to it being discovered by Lark that she's a fae and not a child, leading to a sort of wry friendship.
It's totally up to you. Don't post if you don't wanna. But you don't gotta feel like your character is trapped in a bubble if she's not actively interacting with someone: even stalking is an interaction, when it comes to RP.
Just my friendly personal opinion, o' course. Take it or leave it.