Which Pony outfit are you referring to. The one you need for the early Quest with Nimhe or the one you need for the quest with seraphine?
A related issue has been reported before, it was caused by the use of a mod called urm which corrupted the data. Space journey x cannot be run with urm and once it has been started with the urm code it's irretrievably corrupted.
Did you have this mod installed?
The Pony quest for seraphine kicks off when her exhibition has reached level 6 . You can only start to train her exhibition once she is willing to wear a uniform and has become a member of the crew. She becomes a member of the crew once she has contributed three times to the ship's mission by doing a successful shopping activity.
As this is more or less an optional Quest, it is not visible unless the shopping trigger has been fulfilled.
