The poem is Mad Girl's Love Song by Sylvia Plath. And I forgot to mention a very important detail that might make a difference- the title of the film is actually pulled from the quote.
I would like to use a quote (2 lines) from a poem in the opening credits and possibly promo poster for a short film (film festivals only). Can I do so, as long as I acknowledge the author? Or would I need to obtain permission to use a quote in such a manner?