They sell tracfones on amazon. They are usually cheaper than the unlocked models. Unlocked should work too but make sure you get a byod sim pack as well if you buy an unlocked model.

Not sure how much you want to spend. The Samsung A13 5g is good value at $119 https://www.amazon.com/Tracfone-Samsung-Galaxy-Prepaid-Smartphone/dp/B09X7G4FT4 There are cheaper samsungs too if you prefer. Or she might be better off with an iphone if you want simpler. Walmart also sell tracfones. Pretty much everywhere does lol.

Don't just pull the sim from the old phone and put it in the new one. You'll want to activate it properly using the new sim you either get with the phone or from the byod pack I already mentioned. If you need help with that just let us know.