On that same note. Girl may be "diminutive" (I don't agree with that), it's not derogatory. (Unless you say a teenage girl for someone who is an adult) Even if used intentionally to putdown your subject, it's not effective. ("You're a girl" .. well yes, the meaning of the word is incredibly flexible and doesn't indicate maturity or explicitly state negative qualities)

I don't think women have the equivalent to "boy." Boy is used by women to adult men to degrade the subject.

Even though we have two similar words which may belittle the person, we have another case where the womens' version is watered down to belittle less.

-----

That being said "dude" is a pretty weird neutral term is odd in use, and formality.