Using someone else's art for my poetry.

Hi. This is my first post/question here. I have written a poem that I would like to print and distribute locally. I found a painting in a charity shop by a local artist that I would like to use to superimpose my poem onto. I have tried to contact the artist, as she left her address and telephone number on the painting. There is no answer at her house, which seems empty and her phone is out of service. I tried to contact her on Facebook but her last post was over 5 years ago and she is 88 years old. She is an artist of local significance who ran workshops for classes of 30 people at a time. I would love to collaborate my poem and her painting with her consent as it is perfect and seems right. But the most important thing to me is doing right by the artist.

Does anyone have any advice legally or ethically?