This is a clear case where the abbreviation, which is the most common form used, is clearer than the actual spelling. Most writers will use Mrs. for Misses or Missis (I can not find a definitive answer on which is correct) . Missus is a southern (US) pronunciation.
Miss in context is quite clear, but also serves as an abbreviation for Mississippi, and a failure to connect. miss an appointment, or a pitch.
Ms, is very PC but the spelling it out would be strictly phonetic (ie a crap shoot)
Miz might work in a pinch.
English, you gotta love it.
Rule of thumbs... Mrs. if married, Miss if single, Ms. if you're not sure. See life can be simple(ish).
Yours
Mad Lews