闺蜜情比天高姐妹情比地厚
[guī mì qíng bĭ tiān gāo jiĕ mèi qíng bĭ dì hòu]
'Sisterhood and best friend's bond higher than the sky and thicker than the earth'. The term refers to a close friendship bond between females, where their affection and support are extremely high and solid.