Before altering your lesson plans, it is vital to find out if the student has a reading disability such as dyslexia. Modes of learning for disability-related reading levels vs. uninvolved reading levels (e.g. the student simply never read enough) are different.
If the student has a reading disability, you should consult with the school to ensure that she is able to get the help she needs. Most of the -alexia disorders can be treated educationally. Lesson plans for word-recognition exercises and mnemonics are widely available, and your school should have literature and staff trained to make a dyslexic student comfortable with their learning level.
If the student has no disability but simply has had little exposure to reading, the best method is mentored reading plans designed to expand her vocabulary. Books in progressively higher reading levels can vastly increase word-awareness and curiosity, and even foster enjoyment of reading, which is in itself vital for continued learning. The best books (in my opinion) for this sort of plan must be of interest to the student and preferably written without purple prose or excessive metaphor. Straightforward writing is best: for example, Isaac Asimov wrote books in virtually every subject imaginable and is known for the clarity and accessibility of his prose. A reward system for extra credit might be useful at the beginning, but the goal should be a love of reading in the student so that she does not need external motivation.
It is vital that the student does not feel separated from her classmates; the feeling of alienation can be humiliating enough to prevent any improvement in reading. Many students conceal their low reading level to avoid embarrassment. Normal classes should be conducted with as little acknowledgement as possible, instead simply defining unusual words in the course of teaching.