My sister has been independent of the family since she graduated from university.
(the comma is my own, to break up that horrible string of kanji)
This sentence seems a bit weird to me because there is no verb to go with the を. If I'd written this I'd have gone with 大学を卒業してから (maybe having two からs close together is bad style?). Would this change the nuance?
How should I understand 大学を卒業後 grammatically? Is there a verb elided (I can't see what I could insert that would work)?
Is this structure common? Please could you give some more examples?