What is a person if they are described as a “wet hen”?

Question

In Terry Pratchett's Discworld books (Witches Abroad in particular), the character Magrat Garlick is often called a "wet hen" by at least one of her witch colleagues.

Web searches only yielded the phrase [to be] "mad as a wet hen". From the description there I think it could mean that she is looking for her "nest", meaning she is trying to get a man, but I am far from certain.

From context in the books I am pretty sure that it does not mean she is mad. She does actually seem quite sane, for a Discworld character anyway.

Here are some quotes for context:

Even Magrat had one [a witch hat], although she hardly ever wore it on account of being a wet hen.

"That's 'cos you're a wet hen, Magrat Garlick," said Granny.

Answer 1

In context, I took the phrase to mean dull, drab, a party-pooper.

Then I found this citation:

• [p. 159/139] "'That's 'cos you're a wet hen, Magrat Garlick,' said Granny."

When questioned about the phrase, Terry explained: "Perfectly good British slang. A 'wet hen' is bedraggled, sad and useless. Probably not as useless as a big girl's blouse, though, and better off than a lame duck."