that's not entirely true. What you describe is one way to do it but not the only way. If I was starting from scratch I would recommend a volunteer visa with matching work permit for anyone looking to stay a year or longer. There are BOI companies that also offer to hire you on the books and give you a Non Imm B (BOI) + work permit as well. It costs but it is an option.
if you're working in Thailand, even if it's strictly online for an overseas company you legally require an appropriate visa and work permit - full stop. That they turn a blind eye to those who don't is a different consideration. You don't have to believe me, here's the Chiang Mai Labor Office explaining it
Those from the Philippines quality for visa exempt with 30 days on entry (possibly 45 now with the recent proposed extension). Visa on arrival is a different form of entry - yes, VOA is not currently available but that doesn't apply here.
As others have noted, she'll then have to do 14-days "home quarantine" (the official term used in English) upon traveling to Chiang Mai.