After I outfitted her with souped-up Glass Armor and some fine weapons, I made her Steward of Lakeview Manor. She still had her gear on when she went into the house, but the next day she was mining iron in her civvies. Re: her duties (along with Rayya the Housecarl) to defend the place, does she still have her war gear available?

Yes, she has everything, just not equipped. Grats! Annekke is the most beautiful woman in Skyrim, I choose her as houscarl and follower as well!

A lot of followers tend to revert back to their regular clothing or armor when they aren't following you.

I found something in a Wiki that indicates a Steward will "revert back to her default armor"--which in Anneke's case is 'civvies' / NO armor. As such, I don't see her suiting up for conflict when baddies arrive. I think I'd better go back to an old Save and keep Anneke as a follower. Someone like Jordis the Sword-Maiden seems more suitable as Steward.

And I agree that Anneke is the best-looking NPC in the game. Thanks for the replies.

I have Annekke as steward at Windstad Manor. She hasn't changed out of her armor yet and it's been ages since she took the job. My other stewards for the other manors are custom NPCs but they DO change into their armor right when you ask them to follow you. They don't seem to wear armor if the manor gets a random attack though, at least mine don't.