Charity, You can send her a notarized letter inviting to visit you where you state you are going to be responsible for all of her expenses. She would then take this with her to her interview. As I'm sure you know, getting tourist visas in Mexico aren't easy, but aren't impossible either. My in-laws and sister-in-law and her family all have gotten theirs within the last year. The US consulate in Mexico is looking for the following things: proof the person will return to Mexico, and proof the person has the means to pay for their trip. In the case where you'd be footing the bill, I'd still have her take proof of her parents' bank accounts and/or assets (i.e. houses, cars, etc.) with her, just to show it's not entirely on you.
The US Embassy in Mexico City's website has a lot of good information> Here's that link:
http://mexico.usembassy.gov/mexico/evisas_tourist.htmlI pulled this off of it:
QUOTE
If you intend to travel as a tourist, you should be able to explain and prove how and when you plan to travel, where you plan to stay, and how you will pay for the trip. United States law specifies that you should prove “that is it reasonable to suppose that you will return to your place of origin once you have completed your trip.” In order to comply with this requirement, it is suggested that you present original documents that support your claim of economic solvency. Depending on your particular situation, you may wish to present original, recent bank statements (letters from banks are not acceptable substitutes), receipts of payroll and the pink copy of the Social Security registration if you are employed, your stamped income tax return if you are a business owner, documentation regarding your business, your tax receipt if you own property, your professional I.D., etc. We reiterate: copies are neither acceptable nor necessary.