Has anything been said about her living situation? I initially assumed drug addiction mainly because of her eyes in that scene but there are definitely other possibilities, mental disorder, health issues, etc. She was unreachable for a while before she called, but I know a lot of people who have at one time or another had full mailboxes and they're not mental. Whatever it is, Rose brings it up and based on that conversation it seemed like more of a personal thing than someone else she was afraid of.