Not a girl, but ...

[Cunobelin]

While I'm also not a female, there can be many reasons for a woman to be lactating. One is she could be a mother, and even though her child wasn't there, it could be a regular feeding time, so her body's internal clock is telling her to produce milk. If the woman was say undergoing hormone therapy, this can also cause it. Also a common side effect with medication in women is lactation.