Except she wasn't about to jump. Her thoughts tell you she wasn't. Its was still kinda over the top yes but im pretty sure she wouldn't have. She was panicking and running not really suicidal (see earlier comments)
Why did she go to the top of the building, to enjoy the nice view? Regardless if she had suicidal intentions from the beginning, she could have died if she had slipped. It was extremely dangerous especially since she wasn't in the right frame of mind.
That's a bit dramatic, don't you think? Looking at where she is, the roof is only three stories up at most, and above large bushes. So even if she did jump, at most she might break an arm or get scratched up, but I doubt she'd die.
Yes, a dramatic location for a dramatic climax, but the whole thing was kind of done in broad, deliberately meolodramatic strokes as high school stuff goes. It fit.
Also the first place one would think to run, to get away from the person they want to avoid won't be the edge of a building would it?
You said "think", which is the exact thing she's not doing at that point. The sole thought was "go somewhere senpai isn't". After she's on the roof, she doesn't climb the fence right away, but only when she's trying to put a barrier between her and senpai. Which also has the story function of being somewhere a lot of people could see them. I doubt there was much actual thinking beyond that.