Thailand also has a basic multi entry tourist visa you can apply for easily. You get 60 day stamp everytime you enter and can extend 30 days for 90, then need a border bounce or trip. If you get a 60 day stamp just before end date of the visa you can get almost 9 months
For her to have 1 foreigner as an employee you need 4 thai employees or 3 including herself while running a legitimate business as the work permit for a foreigner will draw scrutiny.
Lots of reasons. Maybe she's got darker skin, is slightly over weight, or has kids from a previous relationship or has aged into her mid 30s. These things would make her less desirable to a thai man, but lots of foreigners don't care. Some thai women like foreigners for the hopes of a mixed child because they find colored eyes etc beautiful. Some thai women like that foreigners plan for the future more and will help push them to be independent. I could go on and on, but in the end besides money it's some cultural difference that they find appealing and are open to.
Did you bring a copy of your lease or residency document, thai license can help? What supporting documents did you bring besides your visa and a passport?