does your horse roam free?
How did she access your neighbor yard?
How far can she go?
Just very curious
It took me a while to piece it completely together too.
Basically: Unbeknown to OP - The gate some how got open on her horses' pasture and at least one horse got out.
Later the neighbor calls that the pool is wrecked and thinks a horse had been in it (above ground pool). OP goes to investigate and finds horse in question is in her pasture (looking innocent), gate is open, and horse has scrapes on her legs. Pool is mangled.
History of neighborhood dogs chasing horses in the pasture. No idea how gate got open.