Welcome to HCM,
Your mother is long term High Blood pressure
patient and must be taking anti hypertensive therapy,
The episode which suffered is minor stroke
or a Transient Ischemic Attack( TIA) as she has fully recovered, most of the population is right handed that is speech is controlled by left half of brain and in case right sided paralysis
occurs speech is also affected.
In her case a sudden rise in BP due to emotional stress is possible.
Her CT scan
is not showing any lesion,Please visit a Neurologist
take proper therapy to keep her damage to minimum and prevent in future.
In such case Blood pressure medicine and anti platelets,Neuroprotective drugs and some neurotrophic vitamins are required.