Toni, if she has any degree of need for the chair, I urge you take one along. If necessary, contact a rental vender in the port city to have one available for the week.
They can be very hard to find aboard. In fact, the cruiseline's default position may be that they're "unavailable" on board. Also, be aware that even though roll stabilizers and such mostly attenuate the effects of ocean waves, there can still be subtle, almost imperceptible rolls and pitches that can throw the most stable walkers off balance.
She will find the chair almost indispensible for traversing the full length of the ship without fatigue. Her safety at sea could well depend on it.
I may dwell on the land, but I live at sea!
Sensation 2/03 I disembarked, but never really left the ship.
Enchantment 9/03 Just had to go back.
Inspiration 3/04 Just have to go back again, and again, and again...