This is the boss battle for Mission 14.
In order to beat this boss, expose the weak spot by devil pulling the hand on the side of the spawn's body. Once the hand is pulled away, you can angel pull yourself to an eyeball and attack. Eventually, a larger eye will open up on the face of the spawn. Angel pull yourself to this eye and attack. The spawn will fall down after being attacked enough and Lilith's legs will be exposed. Devil pull her outside of the spawn's body and attack her. Rinse and repeat.
There is a health bar for the spawn and for Lilith as well. You will unlock the achievement at the end of this mission.