How is your mom? Are there other symptoms present? Stroke symptoms typically start suddenly and in most cases do not progress further. This will depend on the area of the brain affected, the more extensive the area of brain affected, the more functions that are likely to be lost. If there was no trauma to this area, this could be an infection or nerve-related problem (if the lips are numb). You can have this evaluated further for proper diagnosis. Complete medical history and physical examination are important in assessing if other tests should be done.
Take care and keep us posted.