verb/anˌdaɾ ˌkomo kinθeaˈɲeɾa/
to be mutton dressed as lamb
“No sé en qué piensa llevando un vestido así. ¡Está andando como quinceañera!” — I don't know what she's thinking wearing a dress like that. She looks like mutton dressed as lamb!
Literally, “go about as if [preparing for one's] quinceañera”.