After casting that {Fireball}, the first thing Neve did was mark herself and then Thomas.
Once that was out of the way, the battle began.
Thomas became invisible up ahead.
[Into The Shadows? This early? Does he want to try to end this in one quick hit?]
Neve was going to dodge to the right, having to guess Thomas's position. However, Erin's presence meant that she did not need to do that. The lamia dashed behind Neve. Her claws collided with something metallic before Thomas appeared a moment later, backing away.
Immediately, Neve cast {Healing Beacon} on Erin.
MP: 990/1050
She did this so that she wouldn't have to heal Erin actively. Instead, she could put all of her focus on the thing she mainly wanted to do for now. Observe.
She did not see Thomas as a human being. She saw him as just another monster. Thus, the best way to approach this battle was to treat it the same way she would one of those mindless beasts.