why Wordnet dictionary doesn't contain the word 'she'?

Question 1

The answer to this is in the WordNet FAQ (which I just discovered existed), and also in this other question.

Basically, she is a pronoun - a word that kind of stands in place for a noun. Instead of referring to Betty by her name - which is a proper noun - you may refer to her as she.

Pronouns by themselves (without Betty, in this case) don't actually contain any meaning. Some people, like the WordNet people, call that kind of word closed-class words. By design, WordNet only includes open-class words.

From the Wordnet FAQ:

Q. Why is WordNet missing: of, an, the, and, about, above, because, etc. [and pronouns]

A. WordNet only contains "open-class words": nouns, verbs, adjectives, and adverbs. Thus, excluded words include determiners, prepositions, pronouns, conjunctions, and particles.

Question 2

Wordnet isn't a standard dictionary, for example, if you search "he" you end up with the element helium and the 5th letter of the hebrew alphabet as definitions. However, you don't end up with the definition of a noun referring to a man.

My best guess is that "she" isn't contained because it doesn't have a definition of a anything other than a noun referring to a woman. I say best guess because I'm not a language expert so I can't definitively say it has no other definitions. If you look up "he" on thefreedictionary.com though it does have references to helium and hebrew. If you look up "she" it only has definitions related to gender.

tl;dr The reason "she" doesn't exist as a word in wordnet is that, by their rules (or whatever you want to call it) it isn't a word.