1814 First meeting between Princess Charlotte of Wales and Prince Leopold of Saxe-Coburg-Saalfeld
Her Wikipedia article has this about the first meeting of Princess Charlotte Augusta and Prince Leopold, "At a party at the Pulteney Hotel in London, Charlotte met a Lieutenant-General in the Russian cavalry, Prince Leopold of Saxe-Coburg-Saalfeld. The Princess invited Leopold to call on her, an invitation he took up, remaining for three quarters of an hour, and writing a letter to the Prince Regent apologising for any indiscretion. This letter impressed George very much, although he did not consider the impoverished Leopold as a possible suitor for his daughter's hand." The Duchess of Oldenburg is Catherine Pavlovna. She was then married to Duke George of Oldenburg. The Wikimedia caption states 1818 or earlier, but this meeting occurred in 1814.