Cheap Bridesmaind

Hi! I am a bridesmaid for my Friends wedding. She put me in charge of planning the Bachelorette party. So I did. 3 Months ago The price was fine for everyone but one BM. So I asked her the price she was willing to chip in. It was $50. So I took some stuff out. Haggled with Limo companies (the limo is the only thing the Bride really wanted.) and got the price down to $54 not including drinks. I sent out the invitation. The one BM RSVP`d she is not sure she can afford that and that she would have a better idea in 2 weeks. Which is 2 weeks before the party. We are all on hard times with money because 2 of ours friends decided to get married a month apart. If she backs out the price will go up for all of us and we need time to save. What can I do? I don`t want to worry the Bride. This is not the first thing she has complained about. And will not be the last I am sure. Please help She is driving me crazy.