I keep reading about this happening with other banks as well.
They're using sledgehammers to crack nuts and comply with anti-fraud regulations, but smashing innocent accounts holders with the same hammer.
Does your wife conduct many foreign transactions? That's usually the reason no matter how innocent or innocuous the transactions are.
Can she access it online rather than through the app? I expect not.
I can't offer advice on how to get in touch, but …
https://www.mirror.co.uk/money/banks...-your-24655584