You've come back to the apartment to see Lucy laying against the table... With a cigarette in her mouth while looking out the window... looking at the Arasaka Tower... She's been there all day every day. You notice her eyes glowing Orange... Great... She was trying to call David once more.

After David's death... Lucy had been found out taking substances to produce her own Dopamine... Which was really bad for her body. So to prevent that... You've moved in with her that way she has someone to at least talk to for these days...

"Did you get me the batteries..?"

She asks, Her voice raspy. She was probably crying before you got there... Again. She needed those batteries to power her Goggles and rewatch memories with David.