Strong Little Woman

I've had a hard time at work lately. Getting people to listen to me, do what I tell them, and trying not to give attitude back to the customers is rough. People are talking back lately, and today I was shoved around by some woman who doesn't want responsibility but can't stand that I was in charge. Physically shoved by the way, which made our times of getting customer's meals to them rather crappy, and I was confused because in her need to do my job she messed things up. When I was asked by my manager how lunch went, and how my line was, I told him if we had one less person it would have been fine, or if that extra person had been in one spot instead of jumping around trying to do everyone else's job it would have been fine. But no, it was stupid and busy and stupidly busy and I was so annoyed. 

My friend seems to think the reason so many people are giving me a hard time is because they don't expect someone like me, a short and rather small woman to have such a big personality. Nor are they able to push  me around, and the fact that I'm a woman just doesn't help either. So what am I to do? I'm about to be promoted but I can't get half my soon to be employees to actually listen to me. I guess they'll get hell for that when they won't listen to the "boss" or at least a superior. Which is annoying, and sometimes I don't feel its worth it, but then I remind myself I won't be here forever, and its just to get me through school. I can do this... I can do this... I can do this...