It's not likely they will stop her benefits. She is in the age bracket that helps her. Going to college is not the same as working. Social Security would have to do a review of her claim to even have a chance of knowing she is going to college.
It's only one oipinion but it sounds as if she still would be unable to work with her speech impediment and inability to walk long distances. The only thing going to college proves is that she can sit for a few hours and has the mental capacity to absorb and retain information.
It's difficult being physically challenged. I would say encourage her dream.