This is from MY experience (It may not be 100% accurate):
Those that will NOT attack while in form:
Companions (WerewolfFaction)
Housecarls
Hirelings (I tried it with... Stenvar I think his name was)
Certain quest NPCs from DLC's (don't want to give any spoilers)
Those that WILL:
Companions (Those no longer in WerewolfFaction, i.e., cured.)
Guards
General NPCs
Certain quest NPCs from vanilla game and DLC's (temporary followers like in Laid to Rest, from my experience)
Sometimes Housecarls or hirelings will attack you. I think it's due to moral standings, I'm not 100% sure. I've never had a Housecarl attack me nor have I been attacked by a Hireling.
Which follower is attacking you? That's what I'm wondering.