One day you’re just a little girl, the next you’re getting ready to get married. I'm proud of the lovely young lady you've turned out to be.
=== It seems it was just yesterday that you were just a little girl.
How do French speakers handle this hyperbolic, colloquial device used to emphasise the lightning-fast passage of time? Technically, the past tense should be used in the first clause: "One day you were just a little girl". But the present tense serves to highlight the notion of "how time has flied".
When a situation has changed overnight, "du jour au lendemain" does come in handy, but I'm not sure if it's suitable for use in this structure. I wonder if "sans crier gare", on the other hand, is a bit too much?