in her diary of 28 september anne mentions that she is being discussed from A-Z. what does she mean?

Anne is referring to the fact that the adults in the annex are embroiling themselves in constant bickering, of which she is the main discussion. Anne feels as if she is at the middle of every argument.

They criticize everything, and I mean everything, about me: my behavior, my personality, my manners; every inch of me, from head to toe and back again, is the subject of gossip and debate. Harsh words and shouts are constantly being flung at my head, though I'm absolutely not used to it. According to the powers that be, I'm supposed to grin and bear it.

Anne ends this entry by firmly stating that she "won't take their innsults laying down."