Carrie has been through a lot during the past 30 something years. I have direct family members who are bipolar, as is my boyfriend and another best friend. I can attest to just how trying that can be on a person. I have a great deal of sympathy and understanding for people with a mental disability as bipolar disorder, and certainly commend Carrie Fisher on how she is certainly trying her hardest. With the alcoholism and drug use, as well as weight gain... I'm sure we can all see that she has risen above that in the past several years.
Also, she has been in some pretty good movies since- When Harry Met Sally, Blues Brothers... and has roles in others like Sorority Row, Scream 3, and Jay and Silent Bob. She is a regular/frequently recurring voice actor on Family Guy, too. Add her books, comedy shows, tv roles, and script work... and it is safe to say that she has kept herself busy, despite having bumps in the road.
I'm certain she will have a memorably good role in the new film.