I picked up this Orc warrior woman as a follower because I liked her. Is there good reason why she won't wear the full steel plate set I bought for her? Her default armor looks like ordinary orcish wear and she prefers it. What, she doesn't want to match armor with me?

Her Orcish Armor is better than Steel Plate. So, she defaults to the better armor.

Well... lets look at the facts: Orcish armour is better than steel armour in every way? Why would she want to make herself MORE vulnerable to death?