She told Hello! she decided to bring the bouquet because she only had "one chance of meeting the Queen", but was informed by security at the Palace gates that Her Majesty would not accept them due to protocol.
"I think they were very shocked when it happened!" Laura-Ann admitted.
"She smiled so warmly at me and thanked me very much. There were 8,000 people there and I honestly couldn't believe my luck.
"I curtsied and loudly said, 'Your Majesty I have some flowers for you'. Once I spoke and curtsied I don't think she could have walked past me, everyone was watching and everyone heard it! I told her she looked beautiful in pink and she smiled again."
The Queen was joined by her granddaughters Princesses Beatrice and Eugenie for the annual event, as well as her grandson and newly minted dad Prince Harry.
The daughters of Prince Andrew and Sarah Ferguson looked chic in summery ensembles, with Beatrice the picture of modern elegance in a deep hued floral dress by up and coming designer The Vampire's Wife.
Younger sister Eugenie chose a nude dress by Parisian brand Sandro which she paired with her favourite silver Valentino Rockstud stilettos.