Where in the text did you realize not all the narrator is telling you is true ?

I don't think she intentionally lies to us. She goes through extreme emotional swings. Sometimes she lies to herself in the midst of her anxieties,

Dear John! He loves me very dearly, and hates to have me sick. I tried to have a real earnest reasonable talk with him the other day, and tell him how I wish he would let me go and make a visit to Cousin Henry and Julia.