, If you are talking about the visa exempt, she does that the moment she passes through immigration in Thailand. There is nothing for her to apply for. It is a 30 day exemption. If she wants to extend that then she has to visit immigration after arrival and apply for an extension. It is a quick process as long as you have everything they require(which isn't much).
If you are referring to the 60 day tourist visa that can also be extended she has to do that an embassy in her country