The packages are stinky as they are so old, in addition to program versions on offer are frozen several versions behind program versions on modern distros. System76 even started to offer Ubuntu 24.04 on their prebuilds for this reason. It’s too old and while they managed to bring more recent drivers to Pop!_OS, it’s going to be phased out when COSMIC DE is ready for stable launch with an Ubuntu 24.04 base. Pop!_OS is not a good recommend going forward; System76 let it get too old before taking appropriate action, but to be fair to them, building a DE from scratch is hard work.
My only concern would be the specs of the machine; Laptops can vary so much in terms of performance and level of support for the components within it. It would probably work easily using Steam+Proton. I play The Sims 3 using Steam+Proton on my Ubuntu Linux Desktop, the performance is pretty good! It only made my processor a warm 63C to 65C, I played on high specs with shadows turned down (shadows are always resource hog). I had a few packs enabled, but not enough to truly test my system.
The worst hurdle is always the initial Vulkan Driver processing. Depending on the quality and heat management of the laptop/PC that will be used, it might overheat during this process. Afterward, she should have a perfectly normal launch experience. One thing I noticed is that attempting to sign in will cause a fatal error and the game will need to be restarted; cloud saves are not enabled for The Sims 3. You’ll naturally have to back up her saves and transfer them to wherever they’ll be going post Mint installation.