I have a learning disability, in math. I got as far as trig not even knowing. I just knew that it was damned near impossible for me to get anything better than a C in any kind of math class, and I thought I was just plain old stupid. Looking back on it, I just shake my head at myself. I was still getting mostly A in the rest of my classes.
But my first chemistry classes were a disaster. Between the fact that I'd never taken a science class in my life before then, and my difficulties with math, I worked harder for my C's in gen chem 1 and 2 than I did for CALCULUS.
Here's what I'd tell your friend. First, don't automatically assume that chemistry will forcast how well she'll do in any other class. For instance, I did very, very well in every other pre-med class. Mostly A's, a few B's.
Second, most campus's have a student disability department. She should find out whether they have one. After that, many campus's have learning disability testing, and she should go through it. It takes a long time. For me, I was tested on several different days for hours at a time.
If it's found that she does have a learning disability, then she may be eligable for a variety of services that can help her do better in the classes she's having a hard time in. Usually, these services are extra time on tests, taking tests in a distraction free environment, free tutoring in some classes, having notes taken for you, special paper (believe it or not) provided to you by the school (to help you line up numbers - that was one of my major difficulties), and classes to help with study strategy. At a bare minimum, she should take the classes. They were a life saver for me.
Now, all of those services I've listed are really contraversial for those who don't have a learning disability, so if she does have one, and she takes advantage of these services, I advise that she keep her mouth shut about it, except to her professor. It sucks to have to deal with the hostility of your class-mates, on top of having to take the damned class anyway.
I hope this helps,
Nanon