Girls hair with onions may have the following meanings:

1. Onions may represent the emotion of crying or sadness. In the song "Onion", the girl expresses her sadness with tears, which may be a way to express the girl's dissatisfaction with the boy or the pain of a breakup.

2. Onions may represent girls who have not yet gotten over the failure experience of their last relationship. This may be that the girl is still unwilling to accept some things about the breakup, or is still struggling with whose fault it is, while the boy has already gotten over this experience, and the girl is lingering on some small emotions.

3. Girls sending onions may also mean that girls dare to love and hate, and have the courage to express their anger. Onions can make people cry when they are cut, which can be seen as a form of emotional catharsis, and girls may express their emotions in this way.

In short, the specific meaning of girls hairing onions may need to be comprehensively understood based on the specific situation and the girl's personality and psychological state.