The fights have RNG. The first time I fought the Scythe girl she wiped the floor with me but the second time I fought her she was pretty easy to defeat as long as you anticipate her strong attack that dealt 100 damage.
As long as you survive that attack and fight her aggressively without being too reckless with your health it should be an easy fight.
Also if you want to increase your turns then you can consume that medicine thing
I wish this game had the same turn based gameplay as SCP expedition game