My mother wakes up my brother (baligh) for fajr everyday. She tries to wake him in a calm way however he doesn’t wake up and it ends up that my mother is just forcing him to wake up every morning. It comes to a point where she is nagging him and it seems like he is beginning to hate the prayer itself as she comes into his room multiple times to wake him up and they sometimes begin to argue etc. Please can you advise whether it is correct to keep nagging in this way as I fear it is causing more harm than good.

It should be done in a nice way. Conversation must take place during the day on importance of Salah. There are tips on how to help our children pray. Please see my video on Noor Islamic education YouTube channel