...I know Tabitha wasn't trying to leave, but her exit from Fromville (AKA "the island") made me think of this thing I wrote earlier on in the second season:
If they all get to leave Fromville, they'll do it by walking out together, as a group. Maybe it would look something like a biblical trial or a mythical quest, calling back to Father Khatri and Ethan's speculation about the place.
An individual trying to leave on their own is not ideal.
Nobody who arrived in the town had any indication that they were entering a weird/supernatural/whatever environment before seeing the tree. Why would a person have any forewarning before leaving?
Let's put aside the increased resistance the town and woods kick up when trying to leave. Let's for a moment pretend you don't encounter weird spiders, lighthouses, chained up creepy dudes, and skin worms when trying to escape. Let's say if you just keep walking you'll eventually just walk out.
What then? You don't know how to get back. You've left everyone behind in a place you don't know the location of or how to get there. And you, yourself, have been a missing person for months or years. What are you going to tell people?
Will you tell them the truth? Will you tell them that you have been in a magical town that's impossible to leave that's populated by monsters that obey vampire rules as long as you have a super special rock on the wall of your house? Oh, and by the way, I can name dozens of other missing people from across the country... some of whom disappeared after I went off the grid. Is that what you tell people? Because it sounds suspicious as fuck.
Even if they can't pin the blame for anyone's disappearance on you, your story is so insane that it will not be believed. No one will help you try to find the other missing people. You might very well become a person of interest when future people who missing under similar circumstances.
If you manage to walk out of the woods alone, you're fucked.