I don't think it's up to you to decide what product to use on this clients marble floor. If you make this decession for her, you'll be held responsible for the damage, if any.
Marble floors usually get done by floor professionals who use lg. buffer machines....This is not a job for a cleaning women.
If she's home when you arrive, ask her what product she wants you to use on this floor to get the results and finish she wants or leave her a note asking her this if she not home.. Until she leaves you a product to use for this, vac (((using the flat attachment...don't use the beater on it.))))) and then DAMP MOP this floor only with a very mild cleaner mixed with very hot water....rinsing the mop often, ringing the mop out well.....then before it actually dries, buff it up with a clean soft dry rag...have lots of those on hand. Don't allow this floor to dry on it's own as it will end up looking like someone spilled soda on it and forgot to wipe it up.