一紧张就会咬嘴唇的妹纸
[yī jĭn zhāng jiù huì yăo zuĭ chún de mèi zhĭ]
'The girl who bites her lips when nervous.' It's a very vivid and endearing description of someone, perhaps the user themself, reacting to being anxious or shy by biting their lip. It's both cute and relatable.