What you could do is buy an older iPhone (say iPhone 11 or 12…. 12 mini for example) unlocked (carrier and iCloud) and give it to her. Since iOS 13, you don’t need a cellular plan to setup iPhone now. It’ll behave exactly like iPod Touches all those years ago.
That way, if the iPhone is still receiving updates and she’s old enough to have a cellular plan, just purchase a cheap MVNO plan and pop it in.
Didn’t read the entire thing…
At the end of the day, they’re all Safari on iPhone.
I still use actual Safari because I like the UI and refuse to use chromium on other platforms. Firefox is my backup browser when Safari fucks up