I tend to think that Mary died early on. A 1965 article about the 25th anniversary of Paul Kovatch and his (newer) wife Mary mentions *her* daughter, Mrs. Edward Pinkos, and other children, Mrs. John Valentino and Mrs. Warren Hess. From her obituary and her Social Security application and claim, we know that Agnes Kovatch was Mrs. Hess before she married Mr. Bennethum (her son was William Hess).
For a bit I thought that Mary Pinkos could be Mary Kovatch, but putting this article together with others, it seems clear that she was the daughter of Paul’s second wife.
A 1954 article talks about a baby shower given to Mrs. Edward Pinkos, by her mother, Mrs. Paul Kovach (note spelling)—by that time, Mrs. Paul Kovach was Mary—and sister, Mrs. Irene Valentino.
Obituary for Paul Kovach (note spelling), The Mercury (Pottstown, Pennsylvania, 16 Jan 1971 - Sat - p.2: lists his survivors as Agnes (Mrs. Warren) Hess, Reading, Mrs. Mary Pinkos, Spring City, and Irene (Mrs. John) Balentino [sic], Downington. Mary Kovatch Brazel doesn't figure into any of these items. Her absence from the first two articles doesn’t mean that she was deceased then, though; she may have been institutionalized, as your family believes, living far away, or estranged from the family. But I think she would have been mentioned in her father’s obituary if she was living at that time.
Other details from Paul’s obit: his wife Mary’s maiden name was Slinski; he was born in Zahor, Czechoslovakia*; and his parents were Paul and Annie (Branie) Kovach.
*This part of what is now Slovakia was part of the Kingdom of Hungary when Paul was born.