So I fast-travelled to Whiterun the other day, with Serana in tow. As I'm heading up the steps to Dragonsreach who do I see? Serana, coming out of the main hall doors walking towards me. She's wearing her original vampire lord armor. So I turn arouind and see MY Serana still behind me, wearing the set of armor I gave her. (I have no armor mods running, just using vanilla game stuff)
I spoke to the 'new' Serana, she has a whole different voice, completely different voice-actor set. She then casually wandered down to the market district and proceeded to 'shop'. That is until I finally went down there and disabled her via the console.

Ever heard of this happening? I only just recently installed a few mods, this one being one. I have a few other small ones, like marriable female npc's, Paarthurnax dilema, guard dialoge, etc. Nothing that should affect Serana like this.