According to the Oxford dictionary
behave [intransitive, transitive] to do things in a way that people think is correct or polite
Will you kids just behave!
She doesn't know how to behave in public.
The children always behave for their father.
behave yourself I want you to behave yourselves while I'm away.
My idea is that
If we treated language like math, could we say?
because if we replace the verb "behave" with "to do things in a way that people think is correct or polite", the sentence will be
-"She does things in a way that people think is correct or polite".
However, "she behaves" doesn't make much sense and like examples in the dictionary, we need to add more words, for example,
"She knows how to behave" or "She behaves well" or something like that.
Is it correct to say "She behaves" or "She behaves herself"?