This might be an obsolete documentation part. When it is time to have the uniform registered, you just talk to Tris and the cut scene will play.
Of course, that is assuming that you did the initial visit to station control to ask for uniform registration.
Giving her the uniform is not enough. You must increase her exhibition stat and you can do that by doing station walks having her wear the uniform. I think. The process is described in the walkthrough. Let me know where the description was misleading and I will update the walkthrough.
Also, make sure to have a look at your quest log and any open activities that are related to that. There is a hint for each activity step which usually gives more information.