Although Faith here was years before when Vi knew her, she still felt the same need to help her that she would have the woman she knew. She'd stood beside them in the battle for the Hellmouth, laid her life on the line like the rest of them. She had volunteered to help get Buffy out of that building and away from the demon, and give Pike and Andrea a chance to send that demon right back where it belonged.
She couldn't help but silently fear what condition they would find Buffy in. As more people gathered to form the initial invasion, Vi paced, listening to the voices around her, trying to figure out what they could expect inside, the plans to rescue and exorcise. She tossed a bottle of Holy Water, one of a few she had on her person, from hand to hand.
She was ready to pound on a couple of demons. However many were inside, they'd figure out a way to divert them and get Buffy out. The others would find a way to trap the possessed Faith. She stopped and tucked the bottle in her back pocket before making sure the knives were in their places.