Bachelorette Party Attendance?

I am a bridesmaid and I do not want to attend the bachelorette party. Aside from the fact that one of the activites I am not comfortable with, I am MOH for another friend's wedding (which is only 3 weeks prior to this one), the dress for the wedding where I am a BM cost me $270 (we haven't even gotten shoes yet, and this does not include alterations), and then the MOH sends out the itenirary stating the night will cost everyone about $120 apiece. I can't speak for all, but I was not consulted about anything concerning the bachelorette party, nor was it ever asked about anyone's personal financial budget before making all the plans (even has us chipping in on a rental- was it ever asked if anyone had access to a SUV?). I have told her MOH that I would not be able to attend (as this weekend will have to be funded out of the same check I need to pay my car note and credit card bills- and still would have to get hari and nails done for the wedding the same weekend). Her MOH was just like, "You have to come". On top of all of that, the bride wants us to go out on Thurs night (I work all day Thurs), and Fri is the bridal shower and bachelorette party (since the bridal shower is earlier, I will have to leave work early to attend- I'm hourly so that dips into my money), Sat is the rehearsal/rehearsal dinner then she wants us to go to a karaoke bar after that and Sunday is the wedding... I have been having problems w/my feet where walking/standing after a while becomes an issue. There is no way that I can attend all that she has planned and have a smiling face come Sunday- I know I will be in pain. I don't want to disappoint her, but I don't want to run myself ragged or broke...