A strobe light doesn't have to make noise to be distracting. Her attire has the same impact as a strobe light.
Not if you are not looking at it.
Once the ceremony is on and everyone is seated her outfit would not have stood out in the crowd, unless the crowd made a point of staring. If they choose to do so that doesn't make her rude for wearing an outfit that is typical for her, anymore then it would make someone rude for wearing a Sari, a kilt, a kimono, etc.
I think the difference is this:
Scenario 1: Person in a sari
Graduation Attendee (glancing idly around the audience): *thinks to self* Oh, wow, what a beautiful sari! (admires for a few more minutes, moves on, focuses attention back on ceremony. Perhaps points out sari to friend, but it is a minimum distraction to both of them)
Scenario 2: Lady Gaga in outrageous getup
Graduation Attendee (glancing idly around the audience): *thinks to self* Geez, what is that woman wear...holy cow, is that Lady Gaga?
*elbows friend and whispers* Hey, look, I think that's Lady Gaga!!!
Friend: Oh my gosh, you're right! *elbows other friend and points* Look, it's Lady Gaga!
3rd Friend: CRUD MONKEYS!! GAGA!!! *elbows OTHER friend* Did you know Gaga is here???
etc., etc. until pretty soon most of the audience is focused on trying to spot Gaga, rather than on the graduates.
So I think there is a real difference between someone wearing garb indicative of their culture, and a celebrity (who is likely already going to attract some notice) dressing in a manner that is likely to attract EVEN MORE notice at an event that is intended to honor other people.