God bless you and your mom. I understand how you feel because my mother has had strokes and they can be very scary. If it was a stroke, (I am hoping that it was not) your mom needs to be on an anti-platelet medication like Plavix
or blood thinners like Cumidin to help prevent more strokes. The thing about strokes is that they are not totally preventable and once you have had one, you're more likely to have more, no matter what medications you are taking.
The good news is that the brain is Extremely resilient--It can compensate quite well for any damaged parts and some people recover completely, no matter how many strokes they've had. I hope this helps and I wish you and your mom the best.