How much should a Bridesmaid be expect to chip in towards the Bridal Shower?

I'm in a wedding this June the MOH (Sister of Bride) has been planning the Bridal Shower. Originally we were asked to give $100.00 towards the shower. So with 6 of us that is $600.00. Mind you its at a firehouse which is cheap and we are all expected to make a dish. I received a text from her the other day asking me for ANOTHER $50.00 so shes telling us this Shower where the food is being provided by us which isnt even included in the money we already gave is going to cost $900.00 One of the other bridesmaids tried to contact her and tell her it was just too much money and she couldnt afford to give her another $50.00 towards the shower and she responds "Do what you have to do" with no other explanation... I dont even know the details of the shower, the theme, anything! The only time we hear from her is when shes demanding money from us. I just feel that $900 for a Bridal Shower is just too much... ecspecially since we are all providing all the food. So I've given $100.00 already plus I have to make a dish for x amount of people and then buy a gift... Am I wrong to not give the extra $50.00 thats shes asking? Because if I do I'm going to end up spending like $250.00 on this shower? (Thats not even including all the other costs we have coming up too) And so are all the other girls. I just want someone to let me know if we are being unreasonable and if it would be rude to not give her the extra $50.00. We've even asked her to get together with us so we could sit down and try to cut down some of the costs she has figured out...