It sounds like she has managed to install a "launcher" app.
To explain, your homescreens and app drawer are not provided by the operating system, but by an app called a "launcher". The phone will come with one provided by the manufacturer (many manufacturers have their own launchers), but you can replace it with another one. Many of us do this just because we think there are better launchers than the one the manufacturer provides - I always do this myself. But since they manage the homescreen a launcher could add a non-removable search bar or "feed" (actually one reason I got rid of Google's launcher immediately on my old Pixel was because Google included a search bar that could not be removed - obviously that one was a Google search bar, but I'm not standing for some corporation telling me "you have to have this on your screen").
How to get rid of it? Go into the system Settings and search for "Default apps". What does it say for "Home app"? Samsung's default launcher is called "One UI Home". If you see something different, click on the name and if should let you change the default launcher. Take a note of what the current one is, because you probably want to uninstall that afterwards.
Another way is to go to the Play Store and install another one (I use Nova Launcher). Then when you next press the home button/use the home gesture it should offer you a choice of home apps (launchers). But the method above should work (I have a Galaxy s21 running Android 12, so I expect what works on my phone will work on hers).
If it says that One UI home is the default home app then there's something very odd going on. One thing you could do is boot into "safe mode" (instructions can be found
here). That disables all user-installed apps, so will give the normal home screen back, but obviously also means that any other apps she's installed would be disabled. The purpose of this mode is to give you a stable phone while you identify an app that's causing problems and remove it, but you should be able to do that without safe mode. However if it isn't a launcher (i.e. if it's something that's somehow drawing over the home screen) and so harder to identify this might be a helpful option in the short term.
I'm hoping it is a launcher that has been installed inadvertently, because that will be the easiest thing to identify and remove.
Worst case: there's no other launcher visible and safe mode doesn't change it. At that point I'd worry that her service provider has included a modified version of the default launcher in a system update (I've no idea who Fonus are, but I put very little past US providers from the things I read in this forum
). If that's the case then installing another launcher (and setting her home pages up again using that) would be the only way to get rid of these things.
