Sweet Release is a tier 1 skill in Maya's Harmony skill tree. Killing an enemy who is currently Phaselocked creates life orbs which seek out and heal you or your friends. The healing effect is stronger the lower you or your friends health is.
The maximum possible healing only occurs when Maya is almost dead (around 1 hp, or close to it). Another way of looking at it, is that each orb heals 15% of her missing health. If she has 40% health left (60% of her life bar is empty), an orb would heal 0.15 of that 60%, which means 9% of her max health is healed.