It didn't seem clear in the movie, but maybe someone who has read the book has more information on this.
It seems like Prudie's mother's traffic accident may have been purposeful.
I think she was probably high.
We accept the love we think we deserve
http://mrsantonyelchin.tumblr.com/
The book doesn't really expand on it except that Prudie is preparing for the session she is hosting and then Dean rings her and tells her that her mum is in a bad way and sort of hints at the fact that she won't survive. Then the next thing we hear is that Jocelyn has brought a sympathy card for every one to sign. I would actually say it's more explicit in the movie than in the book.
The Baroness: There's nothing more irresistible to a man than a woman who's in love with him.