天然萌幻想系洋娃娃
[tiān rán méng huàn xiăng xì yáng wá wá]
This username combines the idea of being cute, innocent (天然萌 'innocently cute'), with an imaginative and fanciful personality ('幻想系' meaning fantasy-oriented) that the person describes as doll-like. It suggests the user views themselves as playful yet dreamy, living in a world somewhat apart from reality.