Thank your for submitting your item for appraisal. This appears to be a small tondo, oil on canvas laid down on board, depicting a young woman in a red dress with red gladiolo in front of a blue background. The artist Mary Black Diller is hardly known. She apparently lived in New York and Pennsylvania and published a book "drawing for young artists". I would advise you to have the painting restored, the paint is flaking off and this might increase over time. Ask your local museum for a list of qualified restorers. The estimate is based on auction results for similar paintings by lesser known artists. There is no measurment for the sentimental value you might attach to it.