Every time I turn around she has mysteriously donned studded armor that wasn't in her possession prior to...this is a glitch. I have to reequip her ebony suit and pull this studded out of her inventory.

After a few mins I have 4-5 studded armors that didn't exist before...anyone have this happen?

she might be picking up stuff you dropped, ive had farkas giving me back some iron arrows i tossed somewhere saying 'you left this over there, you want it back don't you?'

though i dont know why she would equip it over ebony armor

Maybe she's telling you she thinks your a stud?
But that IS odd. As flabber said, she could be picking up things you've dropped. Or perhaps it is just a bug. Very strange ...

Some followers always equip to their (not available in inventory) default equipment after a time. They usually equip the good stuff you have given them if you remove any item at all from their inventories. Kharjo is terrible for this, for example.
If she keeps spawning them, though, yep, sounds like a glitch.

[Perhaps a dodgy script in the same vein as the replicating Museum keys?]

Sounds like a mod glitch. She actually defaults to heavy armor so studded armor should never be her preferred armor.

If you are on a PC, I recommend downloading the follower overhaul mod. It makes all of the Followers' hidden items visible, and allows you to finally remove them once and for all.

The follower equipment mechanic in this game is well-intentioned, but quite flawed.

I find leaving 1 thing belonged to them in their inventory helps with keeping them in what you put em in, until you dismiss em. If they have an iron sword and shield in their inventory but you want them to use ebony, leave their stuff in their inventory and give them the ebony stuff, this seems to solve them switching back( for me anyway). If you dismiss em then the next time you talk to em you will have to remove and reequip one piece of what you gave em so that they use it otherwise they will revert to their default equipment.

Except that her default armor is Banded Iron and her armor skill is Heavy, so she shouldn't be wearing Studded at all since it's both Light-class and of inferior quality to Banded Iron.

It sounds like the OP ran into a glitch with a script that strips armor; there is a known issue where such scripts sometimes take default equipment and them do not return it later, and if this happens the follower will use whatever low-end armor they receive that is closest to their normal default as their new default, even if it's not the right class.