I have Aranea Lenith as a follower - primarily because she can cast some of the most powerful Conjuration spells and she has killed a dragon on her own more than once.

however, I cant seem to get her to dress like a mage - she wants to dress like other followers with weapons, armor,etc.
But when I give her a mage robe - she wont put it on . Recently I got her to put on Robes of Eminent Conjuration - but soon after she took them off and was back to her normal no bonus clothes.

Of course, giving her only a helmet can be entertaining for a while

Does anyone know how to get her to wear Robes and which robes she will wear?

I wonder if you'd have to pickpocket her current outfit and replace it with reverse-pickpocketting using the other robe you want her to wear.
Check out the wiki page if there is something helpful http://elderscrolls.wikia.com/wiki/Aronea_Lenith#Bugs.

If you are on the PC, you can use the program http://skyrimnexus.com/downloads/file.php?id=4554 to create a quick mod to just either 1) remove her default outfit or 2) set it to what you prefer. But if you have her carry armor loot she'll still put that on, at least until you remove the loot when you want to sell it.

On the xbox - she has the outfit and some times I start the game and she wears it - but when I give her stuff to carry and then take it away - she doesnt put the item back on.
Frustrating.

You'd have to have the pickpocket perk to steal equipped items..... Followers have gear you can't see or take normally and will only equip what you give them if it has BASE stats better than what they have. Enchantments make no difference. Since all clothing is armor 0... it's NEVER better than their default (also 0 armor)

So you need to REMOVE their default gear.... and the only way is with the aforementioned perk.

That... or equip them with something with a higher base value. In which case you can equip her with ANY light or heavy armor and she'll wear it. You can enchant it up for her to give her cheaper conjuration casts.... more magicka, etc. to have her properly decked out.

You might think of improving and enchanting forsworn armor for her

Any armor you like the look of works.... nothing you can do about non-armor apparel though... they'll only put on rings and amulets unless you strip them

Im level 45 and have never pick pocketed with this character ever. I dont want her to wear armor - just a robe - so its getting her to equip a robe if its the only thing I have given her that is the problem.

From http://elderscrolls.wikia.com/wiki/Aranea_Ienith

"Aranea seems to only wear armor with a helmet. She will swap out of her robes for a helmet, but not a chest-piece. However, if given a helmet, she will also put on the chest-piece"

I can't even dress myself.

Sigh.

companions only wear items that are stronger or more defensive than their previously equipped items.

You would think she would put on the Archmage Robes if its all she is carrying - but what do I know. Curretly when I load the game she has the robes on but after I give her anything else to carry and remove it - she never puts them back on. Its seems intermittent and a bug.