Why does this happen?

So I was sitting at the lunch table with this girl I don't really know to well, but I've had her in a few classes over the years that I've known her. We don't hang out or anything and see each other for only about 1 hour and only during school. So I was sitting down minding my business when she starts talking. This isn't unusual as she usually talks about stuff that I don't give a shit about, but this time she went too personal.

"I almost had a seizure on Monday so thats why I wasn't here if you were wondering. And it really sucks because my sister has  and she's having surgery to fix it on Halloween and she loves Halloween."

I'm just there staring at the table wondering what the fuck I'm supposed to say. I wanna say "oh man that sucks" but when I say it it usually sounds like I'm being insincere so I tried to avoid that. I don't wanna bring up some diseases that my brothers or family has because then it'll be like I'm making a competition of it or something. So i just sat there and said "oh man that sucks." and she said "yeah". That was fucking it. That was the whole fucking thing.

Does this happen to anyone else too? Thats some really personal shit and I don't really care. Hell I got problems too and I want to talk to them with someone but that ain't gonna happen. Does she want me to feel sympathy for her? What do you say to in a situation like that?

You tell her that she could go to the surgery place and have a halloween thing there, then she'll invite you and it'll all be cool. THEN you whip it out and tell her it tastes like candy and the hospital ridden sister too.