I'm a bridesmaid and the Bride and Groom could care less about the wedding!?

I was asked to be a bridesmaid in a wedding that I have to purchase a plane ticket for and buy a $150 dress. The wedding is June 16 and the Bride and Groom haven't done anything. The groom told his mom to cook hot dogs for the wedding party and the Bride said that there will be no reception. The groom doesn't have a tux neither does the groomsmen and there are no rings. They have literally done nothing except set a date and pencil in the date on the church calendar. I am good friends with the Brides Aunt so she is trying to plan this wedding and get everything straight and all the bride keeps saying is I don't want to talk about it, its stressing me out! I am seriously thinking about backing out because why should I spend over $400 on a wedding that the bride and groom could obviously care less about?

It is not a matter of the food its the effort she is putting into wedding. She didn't even buy the invitations! 2 months ago her aunt and I had a talk with her about planning and she cried saying we were stressing her out. Then when she picked out the bridesmaid and maid of honor dresses for us she says oh I guess I need a dress too huh? So she finds a dress on craigslist buys it and now she doesn't care about decorations, music, none of the groomsmen have a tux or has been fitted for one she said they can go in and rent a tux 3 days before since that is what her fiance did last year at a wedding. And if they don't get a tux then they are not in the wedding. She said she's inviting 175 people and not feeding them most people have to travel from out of town to come to her wedding. She hasn't sent out the invitations that her aunt purchased 3 weeks ago. She doesn't think she needs a wedding rehearsal, the cake hasn't been ordered, no decorations, nothi