Hello, My 83 Year Mother Has Developed Blisters On The

Hello, my 83 year mother has developed blisters on the inside of her mouth. They erupt on their own and leave blood deposits under the mouth lining (skin). They do not hurt even when eating, except when eating or drinking something hot. It has been 4 days since the blisters first appeared. Her left eye has become red with little or no burning. She does not feel "normal", but goes about her regular routine. She is a "worrier" and just before the incident drove herself to her dentist appointment (80 miles away) with some stressful driving due to some bad weather. Can stress cause such blistering?