The Duff Gordons did not carry suitcases into their lifeboat. That’s just a rumor, one of the many that dogged the couple in the wake of the disaster. Lucy Duff Gordon carried only a small velveteen jewelry bag, carrying what little jewelry she had with her in her cabin. Her most valuable items were in the ship’s safe, including a $50,000 (uninsured!) pearl necklace from her jewelers in Venice, which she had only "on approval" and did not actually own . She had to pay the sum out in installments after the loss of the necklace, so she eventually did own it. It must have been an aggravation to have to pay off a fabulous piece of jewelry that you’d never be able to wear! But at least she was alive and not at the bottom of the sea with the necklace.
As to the story that the Duff Gordons were seen in various changes of clothing on the Carpathia
, I’m sure you have got that from Rene Harris’ account, published in the 1930s. Rene had been a friend of Lucy’s at the time of the disaster but in later years they quarreled. I believe Rene’s comments about the Duff Gordons in her article were colored by the spat she had had with Lucy.
The truth is that the Duff Gordons did have changes of clothing, but these were supplied by the Carpathia passengers who lent them the use of their stateroom. Many people were helped out in this way, so there’s nothing odd about it.
By the way, the kimono dressing gown Lucy wore off the ship was lavender with a mauve and silver Chinese floral print. It was incidentally not one of her own designs but was bought from artist Mariano Fortuny’s studio in Venice. (The Duff Gordons had spent Christmas 1911 in Italy)