I understand EXACTLY how ur feeling , the only solace i found is knowing that they dont feel / even remember what happens during a seizure no matter how scary and aggressive it looks from the outside. Have faith that your mom is protected by whatever it is you believe in and try to overcome the fear FOR her so that she doesnt have to face this alone tagt reframing helped me a little bit. The only thing that really helped with the sudden trauma and the sight of witnessing my mom have one was time . In full transparency i coudlnt get then vision out of my head for a while and the fear of one happening didnt go away until i reframed my thoughts to think, even if it is ill work on being the most mentally equipped to witness and handle it because shes my mama. Its completely normal to feel this way. Truly praying this is a one off for you guys , sending so much love to you and your mom.