Definitely agree with Kneale on waiting for her to ask, or possibly planting the seed in her mind that prompts her to ask the question. Understanding the motiviation for a child to learn something is one of the biggest keys to being able to teach it to them!
At 7, kids generally don't have the fine motor skill development tuned in to using poles the way a 30 yr. old would. The kids are able to do the movements we would ask them to do, but are often more gross than fine, meaning, exaggerated vs. smooth and effective. I would say this is OK, because getting her to start the movements needed now will only help in the future as the purpose of poles becomes more important in her skiing development.