If she doesn't have strong ties to Thailand, like owning a house, and property, has a solid job, and has been paying Thai income tax for a number of years, and has never been out of Thailand, not counting the countries surrounding Thailand, it will be almost impossible for her to get a tourist visa to the US, and hiring an agent, or attorney makes no difference. The process can take over a year.
If you don't get the re-entry permit for bt1000, then when you return you would pay bt2000 for your new 90 day visa, then another bt1900 for your one year extension 90 days later. With the re-entry permit you pay bt1000, and eliminate the bt2000 to start over with the 90 day visa extension.
You don't need an expensive lawyer. A simple visa agent will work. You are aware it is the easiest visa extension to get. Thai Visa Centre is very good