Pathfinder 1E Bramble Break DC

Good Day y'all. I'm trying to figure out a break DC for a wall of brambles. I can find the table for walls and doors, but I'm having trouble finding break DCs for more naturally occurring obstacles. Specifically, I'm running Rise of the Runelords and I know I have a player that is going to try to cast enlarge person on herself while in the [sblock] bramble maze at the beginning of the assault on Thistletop.[/sblock] Since Enlarge Person allows a strength check or you stay the size of the room, I'm trying to figure out what to tell her. Manacles and Chains are only a break DC of 26 and rope is 23. I'm leaning towards placing it somewhere in between those.

A Wall of Stone says this: "If a creature tries to break through the wall with a single attack, the DC for the Strength check is 20 + 2 per inch of thickness."

I'd say for a Wall of Brambles, it'd be more like 15 + 1 per inch of thickness. I would think the character would take damage from plowing through the wall, but the rules don't seem to handle that!