Joan Redfern
From Tardis Wiki, the free Doctor Who reference
Nurse Joan Redfern, widow of Oliver Redfern, was a nurse at Farringham School for Boys, where John Smith was working.
After John Smith became the Doctor again, he requested she join him as a companion, but she dismissed the idea immediately by asking the Doctor, "If you hadn't decided to come here on a whim, would any of these people have died?"
In an alternate future viewed by both she and John Smith, she became his wife, the mother of their two children, and grew old with him.