Take mutagen | Chapter 13 - With the Tide DI Riptide Guide
Last update: 11 May 2016
Don't fight with Harlow any more but head for the room where you have met her for the first time here (screen above).
When you get there, run to the central room and pick up mutagen.
From now on the battle becomes much easier. Wait until the Fury turns on and attack Harlow directly, without letting her to retaliate. Attack until her health drops to zero.
It isn't end, because various mutants and undeads start appearing in the laboratory. Attack them one after another. Luckily, mutagen and Fury allow you to eliminate even the biggest ones without any problems. When the fight ends, listen to dying Harlow and consider taking her Chainsaw.