Form 1: Humanoid
Alexia's first form is relatively straightforward. She attacks with fire and tentacles. Use the Grenade Launcher with Acid Rounds or the Shotgun. Keep your distance and fire when she's vulnerable after an attack. Her attacks can be dodged by running to the side. This phase is a warm-up for the more challenging forms to come, so conserve some powerful ammo.
Form 2: Queen Ant
In her second form, Alexia transforms into a large, insect-like creature. Her weak point is her head/upper body. Use the Magnum or Shotgun. She will spit acid and summon tentacles. Stay mobile and try to get behind her for clear shots. This form can be tough, so don't hesitate to use your First Aid Sprays if needed. Focus fire on her head to deal maximum damage.