It depends very much on what level of learning disability and what level of cognitive understanding and use of language this person has.
I would suggest you try the following:
- very simple language
- pictorial information (i.e. pictures instead of written information)
- short sentences
- symbols
- repeat information over and over, try not to tire or lose patience
If you are trying to teach the Arabic alphabet, perhaps you can connect letters with pictures of things which are relevant to her?
Also bear in mind that she simply may not have the cognitive ability to learn a new language.
How articulate is she in her mother tongue, and how much does she understand?
Can she read and write in her own language?