Text analysis
The poem is about three themes: solitude as the word "untrodden" suggest to me, Nature, as the description of Dove's springs means, and the loss of an important figure for poet, as this lady, named Lucy.
All the poem is written an economy intended to capture the simplicity the poet sees in his friend without cryptic metaphor or a language to difficult to understand.
In the first stanza the poet only introduces these main themes, explaining where Lucy lives, and that a few people know this beautiful place. The images help to make understand the reader about the exclusivity of Lucy, while in the second stanza the poet digs into the innocence of the young lady, during her beauty is compared to a star that shines alone in the sky and to a violet, hidden by mossy stone.
At the end, Wordsworth expresses his pain for the death of Lucy, that was so different to any other maiden he have known, and says desperate "But she is in her grave, and oh the difference to me"!. When Lucy ceased to be, and the poet chooses this verb to underline the deep difference between to live, not necessary in an active and aware way, and to be, that involves all the personality, he highlights the importance of soul richness, despite the adrift of sensibility in mankind.
In particular "ceased to be" reinforce the idea of Lucy's oneness for the poet: it's simply beauty how Wordsworth loved, broadly speaking, this lady, notwithstanding she lived in untrodden ways. It's also a metaphor for the oneness of poetry, that like the girls, can be reached only by people who really like her.
All in all, "She lives in untrodden ways", is a very intense poet, that tell us an experience who everybody have tried during their life, that is the loss of a dear person, and it let us to catch the importance of feelings. Feelings that today are totally subordinated to routine.