That is a matter of preference for the woman. Many would use Mrs. to indicate that she had been married to the father of the child.
If you do not know if the woman is single; married or widowed then you can use 'Ms.' If you know they are single then use 'Miss' or 'Ms.' and 'Mrs.' for married women or widowed women.
Mrs. is a title of respect that may be used to address a married woman. Ms. is preferable, especially if you do not know what the woman's preferred title is, or if you do not know the marital status of the woman.
A divorced woman is a Mrs. If her name is Sally Reid and she was married and now divorced from Peter Reid she is no longer Mrs. Peter Reid. As a divorced woman she is now Mrs. Sally Reid. Those saying a divorced woman is a Ms. are incorrect. A divorced woman, a single woman, or a married woman may choose to use Ms. Ms.basically means "guess" or "my marital status is none of your business."
"Mrs. is the shortened version of the honorific applied to a married woman - "Missus". Traditionally a single woman would be referred to as "Miss.", however in modern times the neutral honorific "Ms." may be used for both married and unmarried women.
Mrs -we used when the woman is married; Ms -we use when we do not know whether the woman is married or not, and we do not want to hurt her.
Mrs. is when a women is married. Ms. is when they are not married. Miss is when thay are younger.
Ms. (pronounced miz) may be used for any woman whether married or single. Mrs. (pronounced misus) is used to refer to a married or formerly married (divorced or widowed) woman in order to specify her marital state. Etiquette does not require either term of address and it is best to use the term a specific woman prefers, if known. If her marital status is unknown then it is best to use Ms. rather than Miss or Mrs.
If the woman is single.
Ms.
The abbreviation Mrs. is for 'Mistriss', the title used for a married woman or a widow. Using the term Mrs. has become a personal matter and a woman should be addressed as Ms. unless she tells you to use Mrs.
The proper salutation for a female can vary depending on their marital status. Mrs. is used for women who are married. Miss is used for women who are single, while Ms. is used for women who are both married and single. This salutation is safer to use if one is unsure of the woman's marital status.
Always use Ms. in the exact same way you would use Mr., unless the woman has specified another title such as Miss or Mrs.