From the first episode and from the first few moments of the present iteration of their relationship Lumière has been telling Éclair "Girls should be more elegant". After working her fingers to the bone to stop a riot without hurting anybody, that comment gets an Ironic Echo from the Smug Snake who forced her to do so. And as Éclair stands there covered in muck, Lumière hugs her ... and tells her that she was very elegant just then.
The entire first half of episode 16, alongside being a huge (and very genuine) Tear Jerker.
The entire second half of episode 20, again alongside being a huge (and very genuine) Tear Jerker.
