I don't think Tifa was checking to see if she's dead (yes that would be hillarious), I saw it as Tifa was going over to her side and putting her hand on her to say her last goodbyes, and then is too overcome with emotion, so she runs out of the room because she doesn't want anyone to see her cry, because she is supposed to be tough.

It doesn't make sense for Yuffie to be the most upset, so I think it's just that she was the most VISIBLY upset. This is because she is much younger than everyone else and much more blatant and extroverted in her emoting.

I haven't actually seen anyone's reactions besides Tifa/Barret/Cloud, but that is what makes the most sense.

MJN SEIFER, you mean to tell me they put a picture of Aeris getting stabbed on the back of the box? Man, what a bunch of morons. But then again, people in marketing usually are morons.