Very unlikely she was originally diesel. Diesel engines had only been put on the water for about a decade when she was built. Smaller vessels had what were called "gas" engines (maybe what later was called Naptha engines?) but ones of this size were normally steam. The steam engines also persisted in yachts because they were quieter, and the fumes were less "noxious" and thus less contribuatory to sea sickness among the guests.

I don't know,maybe she was motor.

Beautiful vessel, was she always motor or originally a steamer?