I can't advise you on a poem to use. Personally, I don't use poems for teaching English for the very reason that native speakers love poems: poetic licence. Poets play with language, alter pronunciation and create new meanings for words. If I had a literature student, I would work on poems with him/her, but I've never been in that situation. I think poems belong in a literature class and not a general English class. The best I can say is to choose a poem whose language is accessible.
You've obviously got a very educated lady here who wants to understand literature and it's good that you are giving her what she wants. Is there any way that she could choose the poem or at least a poet? I'd start with you reading the poem to her or play her a recording if you can find one. You can make some sort of listening activity around this. You can use the poem to work on pronunciation, stress, the schwa, rhythm and to discuss the student's understanding of the poem.
Hope this helps,