Janetfan, it all depends on how you use it and in which context. And it is also important who you are adressing. Some older unmarried women will for example still insist on being called a Fräulein. This is often frowned upon but these women are humored.
Now, generally speaking Medua is right. Good intentions or not (and it is a leftover from the old patriachical days. It is not politically correct to address a woman, married or not, as Fräulein. Not all would perhaps have such strong movements about it but likewise not many would appreciate it either. See, it is even "das Fräulein". A neutre, many girls were referred to as "es/it" in the past. Pretty rude they were in these days.
That is definitely not the case. You can maybe still use it btw to address a waitress.
Just stating the issue...