What Could Sudden Disability To Speak Coherently In An Elderly Lady Indicate?

My 91 year old mother in law became unable to speak coherently at dinner about 20 minutes ago. She is basically healthy - no chronic issues except high bp - and had a check up with her doctor today. She is tired from being out but I can't think of any other event that might have triggered this symptom. It has not happened before. Is this an emergency?