I read that Tessa at the Quincy Police Station had a unique raider power armor arm, Tessa's Fist. I killed her, but she didn't have it, just a PA chest. Reloaded, and tried again, same. Does it not appear on Tessa every time she spawns (each game), or is it not in the game? If I didn't kill her for a quest, is there a chance she will respawn, even though i've [Cleared] the area? I'm lvl 37, so I don't think lvl should be an issue, unless I'm too high, since its a raider PA piece.

3 different playthroughs I've seen it drop from her

And no she doesn't respawn. Generic power armor gunner #3 will spawn instead. Not sure if they'd drop the fist or not.

edit: was well past level 37 on all 3