I wonder whether in the example below:
Peter isn't here today. Martha isn't either.
Can we substitute the second sentence for "Neither is Martha"?
I'm asking this question because once I read in Practical English Usage by "Michael Swan" that one cannot use "neither" here as an exception. (I can't exactly recall the rule!) While we can say:
Peter didn't pass the exam. Neither did Martha. as well as "Martha didn't either."
Please kindly enlighten me.