the toddler wars

Today has been a really hard day for me. My little baby has started talking back and saying no, and today, she didnt want to share with her friends. I knew this day was going to come, and I knew that from us being at the Y that she was going to pick up on some habits that I didnt like, but I thought that maybe it would be walking around with her food or something easy to fix. How naive of me, lol. I feel like such a bad mom today. The whole world is watching my parenting at work, and I just feel like I failed today. I couldnt deal with her, she was driving me nuts. She didnt want anything I had, she kept asking for "dis" (this), but NOTHING was "Dis"! She walked around whining and crying all morning, and I have no idea what she wanted. My heart is deflated. I am out of patience today, especially since today is one of our busier days.
I am a little frustrated because I know how to discipline a room full of two and a half year olds, but I cant seem to figure out my one one year old. Is it just her age? The screeching and yelling are not something that I want to tolerate, but at this point, I dont know where to go with this behavior. I tell her its not nice, but I thinking that maybe I need to ignore it? I DO NOT want her to turn out like some of the kids at the Y...and she sounds exactly like one of them when she tells me no.
And then there is the eating...how do you explain to a one year old that just because other people are eating, you dont need to eat? She wants to snack all morning, because there are constantly people snacking at work. This wasnt too bad for a while, we were kinda on a schedule, but now she is unhappy with what I have brought, and isnt satisfied with anything. I dont have time at work to walk back and forth to the lunch box to figure out what dis and dat are! Argh.
Okay, I think I am done ranting for the night. Hopefully tomorrow I will wake up with a better attitude and a fresh new outlook on what to do with her. This is by far the cutest, rottenest, most frustrating, most rewarding phase of parenthood yet.
Its a constant battle of wills, and I think that today, I am losing :(