My mum won't pray towards the Qibla – need advice

Assalamu alaykum. So, we moved into this apartment back in 2018, and the landlord told us the Qibla was towards one of the windows. I grew up praying that way and never really questioned it until a friend came over about a month ago. She used a Qibla app and prayed in a different direction. I downloaded the app myself and saw the truth – I've been praying wrong all these years, facing northeast. When I told my mum, she got really upset and started shouting, saying I'm wrong. I feel awful because she's very religious, and this would mean all her prayers were invalid. She just won't listen to anything I say, insists the apps are wrong, and says I'm too young to understand. What can I do? She's so stubborn and unlikely to hear me out. She also thinks the government is deliberately changing the Qibla and won't seek help for these ideas. Please make du’a for her.