Snowy,
It's a good thing that she told you and means that she trusts you not to be judgemental about her problems. I have attended many meetings where a person has picked up a white chip. This white chip signifies one day clean/sober and for a person with some recovery behind them it means they have relapsed. In these open meetings I have yet to hear of one person who was not encouraged to move forward and start over. "Do the next right thing" is a catchphrase used in these situations.
You can learn how to support her by going to Alanon or Naranon and I highly recommend you attend some open AA and NA meetings too.
Read the stickys at the top of the forum page too as they have alot of good information.
Here is a link for an article listed on the homepage of SR that I think will help you too.
http://www.soberrecovery.com/articles/138.html
Offering your support can be as simple as telling her you love her and have confidence that she succeed.
Having just one person like yourself in her corner can make a big difference.