hi, wow, i'm so sorry ... what a difficult time for your family
when i was going through my divorce, probably one of the best books i read was called Rebuilding when your Relationship Ends by Dr. Bruce Fisher. it was very helpful and i believe in the appendix there was a section on helping children grieve the loss of the marriage (i lent out my copy). if you are looking for a book specifically for your daughter, there are a few decent ones out there you could track them down on amazon or at your library (sorry, i don't remember the specific names). if you are looking for specific ideas i may be able to offer some thoughts. maybe some of the moms in the single forum would have good book references as well.
just wanted to add that i found that book for kids - it's called Helping Your Kids Cope with divorce the Sandcastles Way by Gary Neuman - if it's the one i'm thinking of it was good but i'm not sure if it would be useful for someone 12 so you would want to double check.