We have an L/S frame and my SO is 5ft3. There is enough room left to fit a bodyfloat suspension seatpost (something that really made a big difference to our riding together).
I never bothered trying wider tires, that's why I remained vague on that. We are riding 28mm tires (Schwalbe One or Gatorskins). For a long tour we're planning this Spring, I will fit a combination of more solid tires I have at home: gatorskins 28mm, specialized infiniti 32mm and maaaaaaaybe continental touring plus 32mm. There is plenty of clearance left in the frame, but I never pushed the boundaries (never felt I had to for our use).