Ambush with a nymph. (Problem \ "Huge Rasianka \") (Pathfinder: Kingmaker)

I play as a necromancer. I went to the nymph, and there was an ambush. As it was written to take the potion of invisibility. I drank. Bypassed all the monsters. And at the end there is a huge sundew. It is impossible to bypass it, to win too. And she notices me from afar. Help, what to do?