I've been a maid of honor a few times and I can tell you a few things that your bride may be thinking but not say to you.
First, she will probably depend mostly on her maid of honor. But she will delegate a few responsibilities to her bridal party if need be - so make sure you can help her out if she asks because that is part of the responsibility of a bridesmaid.
Also, you will probably have to buy your own dress, pay your own way to functions (bacherolette party, dress fittings, hair appointments, any other get togethers of the bridal party). It will cost you some money to be in her wedding, for sure.
Perhaps the biggest thing is to realize that she is going to be stressed out (from costs, planning, things going wrong) and may turn into a crank pot. This is normal, don't take offense, just try to help her get through it and support her.