Yeah if she can't distinguish AM or PM and she can hear the clock properly, I doubt trying to get her on 24-hour time is going to work either. I don't specifically know of any talking clocks that will say something like "good morning" before announcing the time. There are however large talking clocks with very distinct voices that might help a little if she's having trouble with whatever she has. Unfortunately, we really don't have enough information to help because we don't know what specifically she's missing—whether she forgets or actually can't tell the difference, and whether that's caused by a memory problem or a hearing problem.