Xirl is a gender in which one identifies as a non-binary girl. This can take many different forms depending on the individual. It can refer to someone who identifies in some way as a non-binary girl, non-binary girl-adjacent, or is in some way related to femininity. It can also refer to someone who identifies with some part of womanhood/girlhood but who wants a more non-binary or neutral sounding word because they aren’t entirely a girl or don’t want to be associated with the typical ideas brought up by the word "girl".
The pinkish-violet represents the connection and closeness of this identity to woman/girlhood without quite being girl. Green represents how it is a non-binary identity and how it can be an entirely off-binary/binary-adjacent thing for some people. The white is there to bring the pinkish lavender and green together as a reminder of the genderqueer flag. The grey represents the entire spectrum of possible meanings for this gender and how it’s a grey area with a lot of room for individual meaning.
A flag by @_peach_queen is a mix of nonbinary and binary women flags.