If you do end up postponing Honeyfern's death 'til Battle of the True Eclipse (personally not a fan of this idea, gotta maintain the "anyone can die" vibe I was hooked on in middle school), what long-term effects after surviving a snake bite could Honeyfern expect? Alternatively, how feasable would her canon death be as the impetus for proper Berrynose Development instead of just making him sad for a while? Or is there not enough wiggle room for that?
I mostly don't want Proper Berrynose Development because I love the snotball. How can you not love the guy? He is SUCH a jerk and I love this about him. Never change, Berrynose, never change.
But the long-term effects of Honeyfern surviving the bite of an adder? It depends, but if it was a "survivable" bite, very little! Maybe some permanent nerve pain in the area. If it traveled, organ damage. The bite of an adder causes damage done to the cells it comes in contact with. "Venom-induced necrosis" is the fancy word for it.
In layman's terms, it burns the area it's exposed to like an acid. That's why it's not as serious if it doesn't get injected into a major artery-- it stays in that part of the body and damages it. If it gets into the bloodstream, it's carried to major organs and causes organ damage.
It HURTS though, it hurts and swells and it's VERY painful. Frecklewish being bitten between the eyes would blind her from the swelling. Honeyfern would have a fever and rapid heartbeat for several days.
Don't get me wrong though, an adder bite is a very serious injury, and they're treating this with stinging nettle, not actual antivenom.