It is not unusual to have a decline in baseline health status after each stroke. She needs to be on medications for secondary prevention and since she has some decline in memory, the drugs need to be administered to her daily as she might easily forget to take them or even take an overdose because she didn’t remember she had taken it earlier. She needs to have her heart checked by echocardiography and carotid ultrasound scan. She may have a problem with her heart or blood vessels whereby blood clots have formed and keep being dislodged causing the recurrent strokes.
What you can do is ensure she’s properly evaluated and is consistent with medications.It’s commendable that you are looking out for grandma.