Well an internet search would turn up many places. However, if the issue is $$$, then it is going to be impossible wherever they are. You are looking for an option that does not exist. Getting a cheap certificate in the USA. You have said yourself this is impossible.
The bottom line is that she will need the certificate to get legal employment. Therefore she needs to make a plan. There are some logical options like the father coming over, getting a job, financing the wifes certificate.
You asked the question, but are not happy with the answers. Nothing anyone can do about that.