Barbara's main role is to provide sustain via her Skill. Due to the lack of particle generation, building Energy Recharge to Burst every rotation is not feasible. Her Burst should be treated as an emergency button.

Barbara's Skill gives you a pulse of healing every 5 seconds, every pulse will imbue you with a Hydro status, that means it can be used for status-cleansing (Pyro in specific, while other elements may take more pulses).

Take note that Hydro reacting with Cryo status will freeze you in place, her Skill should be used in consideration of the environment.