我妈妈她女儿最萌
[wŏ mā mā tā nǚ ér zuì méng]
This netizen is declaring the cuteness of the girl who refers to herself. She's humorously claiming her personal charm and playfulness by involving her mom as the third party praising her, meaning ‘the daughter (which refers to me) is so cute that even my mother cannot help talking about it’.