Love the series, but the whole Kira leaving with Helena was terrible writing. Didn't make any sense. The whole scene I was thinkng this is stupid, this is stupid, this stupid. Knocks down my opinion of the show :(
Kids do stupid things, but they sometimes see things that adults cannot. Perhaps Kira saw some humanity in Helena that others could not see. I think there is an emerging theme about redemption in this show, and Helena may be on the verge, perhaps because she knows she caused Kira to be harmed.
As for Kira's condition, in the episode 9 teaser, the paramedic in the ambulance calls ahead to the hospital to say that she is "GCS-3", which stands for Glasgow Coma Scale level 3. Level 3 is the least responsive (worst) level. Can't imagine that the writers would let Kira die, but she is certainly in bad shape at the end of episode 8.
I think the show is starting to imply that Kira has enhanced physical and mental abilities, somehow as the result of the cloning experiments. We see body literally mend itself on screen, as she emerges without even a broken bone from being run over. Her enhanced mental abilities are shown by the fact that immediately recognized Alison as not being her mother and seems to have the ability to read Helena's mind. Kira leaves with Helena because she is somehow certain that Helena will not harm her, and wants to speak with her (as if she sensed that Helena needed a hug to be jolted to realization about who her true enemies were).