It's both dramatic and situational irony 
Dramatic because only the reader and the Prato agonist know that Mrs.mallard is pleased with her husband's death and she was shocked to see him alive but the doctor and rest of characters think that she had heartattack out of joy while she didn't
And it's situational because that the doctor said that Louise died from joy but she died from shock from seeing her husband alive and that her new found freedom was short-lived and was taken from her within an hour