Teacher here...you have to find out exactly where the problems are and formulate oral and written exercises which model the correct patterns. also find examples from literature that she is required to read for school, so that she sees in context how to use the patterns you are modelling.

Singwell gave you good advice. Let's expand it a bit. I just gave this sermon to my ESL class Saturday: You must speak English every day. For now, mistakes don't matter as much as speaking. To succeed in this country (i'm in the USA), you must learn the language. In the grocery store, on the street, at home or work or school, start talking a little every day. Turn off your native language TV shows for a while and listen to English. Don't worry about what you miss; concentrate on what you understand. Practice listening...(It went on for about 10 minutes, but you get the point.) I learned German and Latin using grammar first and it was a real chore. I disagree with those who claim you don't need grammar at all. I do believe that it should come second. Practice sentences so that they sound right. Even learn some phrases as you would lines in a play. As soon as you have a couple hundred words and several dozen useful sentences, start to learn WHY you say it that way. All the rules in the world won't help if the language doesn't sound right. I now tell my ESL students that i don't understand Spanish and that they need to tell me in English. A horrible English sentence helps them more than a perfect native one does. Gently correct and try to get her into situations where she must speak English. Only use your knowledge of her language to define new words and compare structure. I admire you for your tenacity and hard work. It won't be easy, but she really needs this. Encourage her to form English sentences and then kindly correct her, having her repeat the right form. Little by little, introduce rules to explain the reasons. If i may ask, what is her native language and what are your specific difficulties. If you need advice beyond the scope of this forum, you may ask for my general e-mail address and we'll figure it out.