IMHO Weiss is already using dust with her glyphs, much like Blake did on the train. That said, I half expected a Ruby clone to pop out of Weiss' summon xP
It's implied that her basic glyph is momentum, and using Dust can modify that to give different effects (Time Dilation and Holding, namely), but then some of her other types don't seem to require it to be modified, or the Dust is just a tool to make up for her lack of experience, as Winter can activate her summoning glyph despite (for all appearances) not having any dust. It is possible that all of her glyphs are modified versions of the original Movement idea (Time Dilation using Ice, Holding using Earth, Gravity using... Gravity, and summoning using Fire to represent time or Water to represent the past or something), But even so, it is still far more complex than any example so far.
I took that more as symbolic, Winter told Weiss to picture her enemies. To Winter the enemies she had to overcome were Grimm, hence why her summon appeared in the shape of one. On the other hand Weiss sees her enemy as that Knight, which is why that sword appeared. They're not actually Grimm, the summon just manifested in the appearance of one.
I find it interesting that, while most Semblances we've seen are singular and simple, the Schnee Semblance is even more complex than their weaponry. Not only can they use many different types of Glyphs to pull of magic effects far more complex than Dust (Movement control, Time Dilation, Manifestation, and probably much more), it's even directly hereditary. It makes you wonder about their family, or if other Semblances can be expanded in similar ways. It might be interesting to see Blake actually clone herself, Nora shoot lighting bolts from her hands, or Ruby dilate her own sense of time and pull a Neo.