Student or Learner
She must be home by now.
Does it mean :
1- She must be home before now.
2- She must be home now.
If someone is conjecturing, it would mean that the person would surely have arrived home by the time the person spoke the sentence.
"By" is a deadline. It means on or before. If I say "be home by midnight" I don't care if you come home at 10. As long as it is not after midnight.