Headcanon that, some time after leaving the Tardis, Tegan visited a very old Ann Cranleigh, both to reminisce the good times and to give that part of her life a new, bigger perspective.
Out of everyone on Earth in the 80s, the Cranleighs (if they were still alive, which wouldn't be too much of a stretch), were the only ones who met the original celery crew. They knew Nyssa, Adric and a much brighter Doctor. Black Orchid was also the peak story in terms of happy memories, right before everything started going wrong (I mean, murder and kidnapping were part of the story, but, for the first and only time in the 5th Doctor's run, nobody in the crew got their minds messed with, or fainted, or died. Results).