西瓜姑娘你的微笑真美
[xī guā gū niáng nĭ de wēi xiào zhēn mĕi]
This translates to 'Miss Watermelon, Your Smile Is Truly Beautiful.' It combines a lighthearted reference ('Watermelon') with an endearing compliment (beauty of one's smile), perhaps alluding to someone sweet and appealing or expressing fondness towards a friend, stranger, or online persona.