What is the tone of Lucille Clifton's "There Is a Girl Inside"?

Lucille Clifton's poem "There Is a Girl Inside" speaks with an energetic, hopeful, and also melancholic tone. The speaker is an older woman talking about her self-identification as a more youthful and sexually aware girl who is ready for life's experiences. As the poem unfolds, Clifton utilizes figurative language to elaborate on how different the speaker feels from her surroundings.

She is a green treein a forest of kindling.

The "forest" is likely the speaker's surroundings—her peers who appear as "kindling"—dry, lifeless material for other people's purposes. In contrast, a green tree is growing, evolving, and full of life.
Clifton's use of definitive future statements throughout the poem provides an energy and hopefulness.

and her lovers will harvesthoney and thyme

She leaves no doubt that the future will occur as she says—but it's still the future, which brings us back to melancholy, especially with the presumption of the speaker's age. In fact, Clifton does an excellent job combining two often opposing tones in one poem.