Jesus said to her, "Thy brother shall rise again."
If He had said "live again", she would have still
had hope. She knew that he would rise on the
resurrection day, but that would be in a long time.

"Jesus said unto her, I am the resurrection, and
the life: he that believeth in me, though he were
dead, yet shall he live: And whosoever liveth and
believeth in me shall never die. Believeth thou
this?" John 11:25-26

That statement challenged Martha faith.