Slip Question

OK so I went for my first fitting today. I love my dress and when I first purchased it I didnt believe that it needed a slip because it is fitted past my bum.
Anyway today at my fitting the seamstress recommended a slip...and gave me a full one from my hips down.

Does anyone know if they have a slip that only has the crinolin (sorry fo rmy spelling) that begins at the knees down...kind of like a mermaid dress?

Thank you

Like this?

Encore Bridal

Ok does this slip go with this dress?
Or is there a slip that starts at the knee?

Its the Maggie Sottero Rhiana Royale