Looking exactly like a person is usually a Finesse roll, but additional magnitudes "for complexity" are often substituted for that. If your saga allows this, I'd agree that this would be that sort of case.
In theory, the item should have an Intellego component if it is going to generate the different effects - to know what that last person looked like - but some SG's will shrug this off as too demanding. For me, the difference between Ars Magica magic and "another-game-that-shall-not-be-mentioned", is that the latter does "stuff", while AM has building blocks - Muto changes, and Intellego gives information and "perception". Without "perceiving" that last person touched, there is no Hermetic way to get the effect - a ring can't see or remember like a mage can. Meh - in the end, "consistency" is the only truly important consideration, that one spell works more or less like another.
(In that other game, you'd just say "sounds like a 3rd level effect to me - works fine!" and you'd be done. Less satisfying imo, on several levels.)
Regardless, we know that MuIm Base depends on how many sense the mage wants to fool - Appearance, Sound & Smell are Base 3, but if her Lab Total isn't up to par, then either work on that or drop one sense and tough it out.
(Note that if she changes clothing (likely) then Touch might come into play at some point as well. Butcha can't always have it all.)
Base 3, +1 Touch, +1 Concentration, +1 Intellego req, +1 for Complexity = 15 Base Mu(In)Im Effect.
+5 levels for Item to maintain Concentration
+3 more for environmental trigger, so it can do that itself at sunrise/sunset, and we're at Level 23.
+# uses/day (for how many different changes/day it can make, including being renewed over Sunrise/Sunset).
Sounds like with a Mu(In)Im Lab Total of 52, she's got 5 changes/day plus one sunrise/sunset continuation, np.