In the plumbing supply store, we were advised that the length of our future walk-in shower (floor-level, one side open) should be at least 1.20–1.40 meters (4–4.6 feet).
@BeHaElJa
I can’t confirm that... but maybe your friend doesn’t have warm water in the shower...
Ours is 1.2 m wide (4 feet)... and some water splashes out... so I wouldn’t go any smaller than that... 1.4 – 1.5 m (4.6 – 5 feet) would probably be perfect...