What do I say to her?

I am a member of a club and we need to find a way to get more people in it. We are a little branch off club of Rotary (adult service club) and I came up with the idea of tee-shirts. The Rotarian that is our sponser told me to get prices and that this project was all mine. Well my friend is in the club with me and she wanted to go and I had no problem with this. When we got there she undermined everything I said and made me look like a fool. I was so embarred. On the car ride home she started yelling at me about how we were going to pay for it when I had told her repeatedly I was told to just get prices and blew up at me and has almost taken the project completely away from me. I want to continue working on it but i don't want her around it. Can you tell me what you think I should say and who i should say it to. If I talk to my friend directly I really have to be careful shes almost on the edge of a mental breakdown.