...the drama.? It's going to be a long one.

Here is what happened:
I was in my college class today and it was like 3rd grade all over again. There is one girl no one really likes because the only thing she really knows how to talk about is shopping, her boyfriend, and all the stuff she got from shopping. Her parents pay all her bills and even pay her back with their money when she buys something with her own money. She is 22 years old and has 12 credit cards that her parents pay for. Yes, she is one of THOSE. Not unlike Alicia Silverstone in "Clueless". She is not one of my favorite people either but she's never done anything to hurt anyone.
Today, she enters class and goes to sit down in a seat (we do not have assigned seats since it's college and they expect us to be able to behave like adults) and another girl says "Um, excuse me, what do you think you are doing?" The unliked girl of course says she is sitting down only to hear "Uh, these are OUR seats." The unliked girl asks "Since when?" The other girl says "Since the quarter started."
The unliked girl then proceeds to move to another seat.

This infuriated me. I may not like the girl but she is still human and I would not have treated her like she was a piece of garbage. So my question is this: Should I have said something OR would that be just placing myself in the midst of the drama?
I try not to involve myself in other people's business because I have a life of my own that has enough going on in it and I don't need other people's BS cluttering up my mind as well.

When I came home I asked my husband how you know when you are being the hero or you are being the drama queen. After I told him the whole story and how I felt, he said I was trying to put myself in their drama and just create more trouble. This offends me as I try hard to keep my nose out of things like this BUT sometimes the strong have to stand up for the weak, don't they? When they do, how do they know they are the strong defending the weak and not just stirring the pot?

I do have to say, my husband did have a point. After I told him all of this he said that the unliked girl needed to stand up for herself because someone (her parents) is always there to do everything for her. She needs a dose of reality to bite her hard on the butt. I completely agree but that doesn't mean she needs to be treated so poorly.

Sorry this is so long, I just have a lot on my mind and I cannot seem to clear it up by myself so I am leaving it up to you community. What are your thoughts?

If you have made it this far please know I appreciate it and also apologize for any spelling or grammatical errors which may have occurred. Thank you all so much!!
**After reading a couple of answers I just want to reiterate the actual question: How do you know when you are sticking up for someone as opposed to just involving yourself in the drama? Or maybe a better question would be "How do you know when to stick up for someone?"
I thank everyone who has already and will answer!!