Yes, if its correct. Some of the things they say are a guess on their part so I really wouldn’t rely on it. A lot of the information on this site is often out of date or just plain wrong.
Then she can get a Non O visa ‘for Retirement’. Pretty easy from London. It would give her 90 days that she extend for another 30 days at Thai Immigration.
She could even stay 15 months, though that needs money in thai bank (unless you pay an agent) and use Extensions to visit each year without getting another visa. (It would mean paying an agent 12-15k or so each year).
I’m not sure if they’ll give the visa if your flight to Thailand is not out of the U.K. You can ask the Embassy and see, but I have my doubts if you are currently resident in another country.