It's beautiful. Im sure your sis will love it. I like how you have used Flowers to explain the strong unity of two souls and the strong bond that marriage should provide. Nice work. Keep it up.
I too think that its a bit shallow and that you could go into more depth on the flowers concept. Other than that, I think that you're views are clearly shown and I'm sure that your sister will like it. The message is very uplifting, nice work!