We don't do anything using the cell phone. I believe she uses the secure network her corporation installed to do the companies North American (Canada, USA, Mexico) financials remotelyThe Samsung S10 was released in the spring of 2019, so in terms of the life cycle of what majority of the world thinks about with phones, it's ancient, but it's still being updated from what I can tell.
Though doing any sort of exchange of personal data through an app on any phone is really hard to tell if the transmission is actually secure or not. It's not in your face like in a web browser. I believe some app builders have been exposed for this in the past and/or exploited.
I'd even be leary of using any of the pay for use VPN services out there for anything serious. You're better off just going home and doing your work through a known encrypted/https connection, at least imo.