Translation:Mr. and Mrs. Hasselgård are eating at our house tomorrow.
So it wouldn't be strange if I used frøken with an elder woman that I knew to be married?
Oh, right! Thanks! I think we need a proper Norwegian to answer your question then :). It has been debated in Sweden at least, sometimes when you fill in a form you have mark "herr" (married or unmarried), "fru" (married) or "fröken" (unmarried). It feels very old-fashioned.
I was completely lost on the first part and submitted 'Har og fru haselgår spiser hos oss i morgen'. Somehow, it accepted it as fully correct.
In English "Ms" replaced both "Miss" and "Mrs". Since "Fru" is a married woman and "Ms" is appropriate for married women (as well as single), could "Ms." be accepted as a translation?