What can I do for my low IQ daughter when I am gone?

Taking care of her. In general there are only 2 things any parents can do: 1) help the child become better at taking care of themselves, and 2) find someone else to help. Everyone has strengths and weaknesses, and no one can live very well without friends, family, and others in the community. See if you can help her make and improve social connections. Continue to teach and improve her living skills.
IF YOU ARE GONE? Nothing at all! Help her, stimulate her to learn while you are here.