parents don't buy groceries

My sister is getting married in July  8th. Since may 27 (her bridal shower) my parents haven't bought groceries or any food for the house. We don't even have canned soup. My mom will go out for wings, she got her hair dyed for a whopping $400 and got her nails done for the wedding and but she won't buy any food for the house. I have a job and work very miniscule hours due to the economy, im the maid of honour so all of my money is going towards my hotel room ($300/night) my hair and makeup on the day (which my sister won't let me do my own I tried to get her to let me) and also getting my dress altered, paying my bills so I don't go into collections etc. I've been trying to get another job on top of mine but no where is hiring, I've been trying for months and no one has even contacted me for an interview. For the past few months I've been eating pasta with some sauce on it... but we ran out of sauce and now there is nothing. No milk , no eggs, no bread, not even canned food. Absolutely nothing. And when I bring it up to my mom she gets mad and says "sorry I failed you" and then walks away. Like we're starving so my sister can get married, we're starving so my mom can get her hair and nails done for the wedding. I don't know what to do because I work today, have no money due to paying for my dress alterations and have no food to eat at all. What can I do?