Proper Etiquette

My best friend is getting married in June. Myself and the other brides maids are throwing her a shower in May. Many of the bride`s maids are in graduate school (like me) or will be in the near future. We are all living on extremely strapped budgets. The maid of honor does not quite appreciate the gravity of our financial situation. She is expecting us all to chip in at least 50 dollars on a shower gift after covering the entire cost of the shower and various other wedding necessities. I am expecting to spend upwards of $600 on this wedding, which frankly I do not have to spend. I am wondering if it is expected that the brides maids give a gift? I do not want to be cheap or rude but financially this is just an impossibility. I thought that the shower was our gift to her. What is the proper etiquette?

Thank You,

Courtney