Faith in "The Wish" 

Hi DrivesFastTurnsLeftandRight, welcome to Wikipedia.  My Buffy DVDs are in a box, so I can't check them, but I assume you're referring to this scene?  I can't check out the tattoo but I suspect it's merely someone who looks quite a bit like Faith.  Eliza Dushku isn't in the credits, and according to the script for the episode...
We see WILLOW AND XANDER go inside. They pass a VAMP as he finishes draining a girl - tosses her aside.
...there's no mention of it being Faith.  Maybe just a lookalike?