Adding a letter she has started classes will not count as proof. If she wants to use the LINC (or similar) classes as proof of language knowledge she would need to complete at least one term of classes, so that a copy of the completion certificate can be included.I am doing same , submitting BA with medium of instruction English but at the safe side , i am going to register my wife for ESL classes and will submit letter that she has started her english classes as well.
Do you think , that ESL ( english as second language ) letter is good choice at this stage , which shows just she start her language classes?
(It may raise some questions to indicate someone is taking basic classes if they also have proof they completed a degree that was taught in English)