if Fortnite is a crucial element for you, and it sounds like it is, you’re going to have to dual boot.
Games like Fortnite, League of Legends, Valorant, Apex Legends, recent Battlefields, etc aren’t going to work on Linux due to the fact Epic, Riot and EA decided kernel level anti-cheats were their “best” options.
That being said the majority of games work on Linux and especially via Steam.
As far as Distros go Bazzite is primarily focused on gaming. If you want something that will do both gaming and work stuff then I’d suggest CachyOS. It’s fast, very fast, great for both work and gaming. It will give you plenty of options for Desktop Environments on install and I would suggest you install it with KDE Plasma so you have a bit of familiarity coming from Windows.
yeah probably hardware accelration on the browser. could also be the DE/WM you’re using on it.
What desktop environment and/or window manager is she using on the laptop?