Looking at IMDB, I'm also wondering how long she was a single mother.
Spouses
Allan Manings(August 24, 1968 - September 28, 2002) (her death)
Jack Fields(April 6, 1957 - April 1967) (divorced)
John Thomas Baxter Jr.(April 1944 - January 19, 1956) (divorced, 3 children)
Google's AI says she and Tom Baxter separated in 1953, but the divorce was not finalized for a while after that.
"Whitney Blake and Tom Baxter separated in 1953, and Whitney filed for divorce that year. The divorce was finalized in 1955, after more than ten years of marriage.
Additional details about their relationship:
Marriage and family: Blake married Tom Baxter in early 1944. They had three children together: sons Richard and Brian, and daughter Meredith Baxter, who also became a well-known actress.
The split: According to Meredith Baxter's account, the marriage was "on its last legs" in 1953 when her mother filed for divorce. Meredith, who was five years old at the time, described the separation as a moment of turmoil for her father.
Divorce finalized: While the separation occurred in 1953, their divorce was not finalized until 1955.
After the divorce: After the split, Blake raised her three children and later drew inspiration from her experiences as a single mother to co-create the sitcom One Day at a Time. She went on to marry and divorce a second time before marrying Allan Manings, with whom she co-created the show. "