That would be: "היא אומר דבר אחד 'והוא' עושה דבר אחר." The word 'הוא' was only mentioned once, so the word "he" should not be repeated a second time.
I wrote "He says one thing and does another thing" why is that wrong? Why don't you translate the second "דבר"?
Yes, to "say" is more purposeful than to "speak" - it's a subtle difference, but you can, in a sense, speak without really saying anything - speaking is making words whether intelligible or not - "I heard him speaking, but couldn't make out what he was saying."
"say" is the form used in most sentences. Speak is the universal word. "I say we should go to the mall" "It speaks"