I need some help!

Ok so it really isn't me needing the help it is my girlfriend.  I need some advice.  I am the maid of honor in my friend's wedding and she is really going through a tough time.  I don't know what to tell her.  Here is the story.......

My friend and her future husband have been dating off and on since I don't know sixth grade.  So as you understand there is a lot of history with them.  The real troubled time in their relationship was about 3 years ago.  She was going through a phase where she was trying to find herself and find out what she wanted from her life.  As anyone knows your early 20's is a time of discovery and learning about yourself.  At this time in their relationship a lot of feelings were hurt by both parties.  So as it turns out they came back to each other and are now planning on getting married.  Happy ending???? 

Nope!!!  The problem lies in her future brother-in-law(bil).  Now three years ago when all this shit was going down he got very mad at her for the things that she had done.  Bil did not think that they should be together and he really let his brother(groom) know this.  He has all along made his distaste for the bride known.  Now that they are getting married things are really getting sticky.  The bride and groom have moved past their problems.  The bride is ready for this to be over the problem is the bil is not.  They are trying to figure out how/if to include the bil in the wedding.  The mother in law and father in law are starting to get involved and saying that the NEED to have the bil in the wedding because he is the groom's brother and it would look bad if he isn't.  The groom's family is really pressuring the groom to involve his brother and the bride really doesn't want someone in her wedding that despises her.  It is getting to the point that it is causing a HUGE rift not only with the bride and the groom's family but is really affecting the relationship between the bride and groom.  The bride has cried herself to sleep already three days this week.  Please Please help me by giving me some advice that can I tell the bride???  What can I offer as a solution??  How can I help her get through this????  Please help both me and her!!!!!!