Hobbled as compared to what?
It isn't the hardware that hobbles a computer, it is the bloat of the software with perhaps a little planned obsolescence sprinkled in. Swift isn't the performance solution to Objective C.
I don't have personal experience with the late-2010s MacBook Air, mine was a 2011/2012 era MBA. It had 4 GB of RAM and ran the OSX OS just fine. I used it to run Safari for accessing this site (and others) and some 1080i video capture using a Blackmagic Design Thunderbolt 2 capture device. I found the 4 GB it came with adequate for my needs.
If bookworm370's wife's MacBook Air is unacceptably slow with 8 GB, it could be the software loaded on top of macOS. If you treat a Mac like a Windows PC and load it full of anti-Malware solutions or so-called "Productivity" software, it can slow a Mac (or any computer OS) down. Make a TimeMachine backup of her MBA, reinstall macOS using the macOS Network Restore, and import users from the Time Machine backup, skipping software/applications. Restore those from your Mac App Store account. Take this time to reevaluate the applications you run.
If she gets a new MacBook Air, chances are it will have an Apple Silicon CPU, so at least a lot of the third-party cruftware won't carry over during a migration. Again, I would take the opportunity to do a fresh install and migrate data but not software. Get any software from the Mac App Store or reputable Mac Software Developers. Get Chrome or Firefox direct from their download sites, not from a link a "friend" online gives you.