A few years back, I had a chica enrolled in the Belitz school in San Jose and after the first term they suggested they could transfer her to the Berlitz program at the university near my home and also get her a student VISA (and her son). The VISA would be good for up to 4 years whether she stayed enrolled in the Berlitz program or enrolled/attended the local ESOL and adult education program which is free. Also her son could be enrolled in the local public elementary school and receive ESOL education as well.
The things I liked about this program were
(1) That it was handled by Berlitz and they coached her on how to deal with immigration questions, since they had a financial stake in you (me) paying their tuition in the US. (rather expensive)
(2) The student VISA was valid for up to 4 years so long as she stayed in school. Even to get her GED if she's not finished high school or college if she has.
(3) If she flaked out on you and stayed in the US illegally, you would only be financially responsible for just one year.
(4) So long as you don't tell the Berlitz people first of your plan, you can after the first term in the US move her to a Free English language (speak, read & write) school. It's part of the ESOL/Adult Education programs that exist in many states.
(5) And, you and she have up to 4 years to decide if you want to marry.
Before you completely abandon your plan, you might go visit with the folks in San Jose at the Berlitz language school. Send me a PM if you want some contacts at Berlitz.