She likes Smartwool socks. They are mix of wool and synthetic fibers. Good at wicking moisture from your feet making them less prone to blistering. If you experience blistering may also want to look at bodyglide. It's an anti-chafe bar to prevent blisters forming on areas that you're prone to get hotspots on feet. Another strategy to prevent blisters taking an extra pair of socks along. If the pair you're wearing get wet (from water or being to sweaty) you can change to the dry pair.

Cotton is a comfortable fabric for casual and short-term activities. But hikers learn to avoid wearing cotton when possible. You may hear hikers and backpackers use the saying "Cotton kills". What they mean is wet cotton close to your body leads to heat loss and may ultimately contribute to hypothermia. That's kind of an extreme example for someone just starting out. So for you, functionally you want fabric that will wick humidity away from your body. Especially from your feet. Moist feet are prone to hotspots that leads to skin blistering. Blisters require recovery time to heal meaning you'll walk less frequently. Here are articles explaining in more detail:

Why does Cotton Kill?
https://sectionhiker.com/why-does-cotton-kill/#:~:text=If%20the%20air%20is%20colder,if%20you%20become%20too%20chilled.

Why Do Hikers Ignore Hot Spots and Blisters?
https://sectionhiker.com/why-do-hikers-ignore-hot-spots-and-blisters/

Do Sock Liners Prevent Hiking Blisters?
https://sectionhiker.com/do-sock-liners-prevent-hiking-blisters/