She didn't want to keep worrying him. She knew he would be concerned either way, but this on top of everything else was not what he needed. Maybe Ruby's words had stuck a little too much this time, maybe she was just realizing that she needed to back off from depending on him so much so that there was less on his shoulders. Maybe it was both. It was probably both.
"You don't get over it, Sam. You just...deal with things differently. You learn how to stop cutting and do something else when you're feeling upset enough to think about it in the first place." She hadn't exactly answered his question, but she hoped she was reassuring him enough so that he didn't think she needed to be on watch twenty four-seven.