Terrible TERRIBLE Manners!

Yesterday we took Big Boy to the blue park, which has the scary slide. I'd promised him that next time we went to the blue park, I would leave Little Boy home so that I could go down the scary slide with Big Boy.
MrDartt ended up coming with us, and he held Little Boy while I went on the play structure with Big Boy.
The scary slide is a high, twisty, covered slide.
So I climbed up the little ladder with the tiny opening to get up to the scary slide, and got Big Boy on my lap. There were two kids playing at the bottom of the slide, so before we went down, I said, "We're coming down! Excuse us!"
After we'd already started heading down, the little girl (probably about 7 or 8) started climbing up the slide. Let's face it: I'm already too big to be going down this darn slide, and it's nearly impossible to stop myself, with Big Boy on my lap, from sliding right into this little bratty girl whose parents obviously aren't watching her (or don't give a hoot about her manners) even though they're sitting at a nearby table in plain view of what's going on.
So then I said, "Excuse us, we're coming down."
And she said, "You can just go past me. Go on."
And she tried to move to the side.
Of course, the slide is not nearly big enough for two children and one adult to fit through one place. We made it through and she climbed up.
The second time we went down the slide, she did the same thing, only this time, she made it almost three quarters of the way up before we were one quarter of the way down. When we met her, I said, "The slide is for going down."
"I know," she said.
I said, "Why don't you turn around and go down? There are a lot of people behind us, waiting to go down."
Again, she tried to move to the side so we could go past her.
Another kid, waiting at the top of the slide asked her, "Is that your mom?"
I turned around and said, "No, that is not my kid. My kids would not have such terrible manners."
"No kidding, I know," said one of the older girls who was helping a younger boy on the play structure.
The little girl with terrible manners ended up walking back over to her mother after that, getting a drink and sitting down for a while.
Of course, she came back after that and continued her slide-climbing.
I know every kid wants to climb up every slide now and then, but I just think it's so rude that she was climbing up even when she knew other people were going down!
Am I just expecting too much from kids on a playground?