Her remarks here are made after the event, after she has been told that Cruz was the shooter. This is also why she says there's 'another' shooter, because she has been told Cruz was one of them.
What she says isn't contradictory, but she is framing what she saw in the added context of what she has been told happened. The term 'second active shooter' is not a phrase a high school girl just makes up on her own. It came from law enforcement.
Basically her story is that she was talking to Cruz when the shooting started, and that means that at that time, when shooting was ongoing, he wasn't shooting. She, at that time, didn't think he was a shooter, and she says 'I'm surprised it wasn't you', because she didn't see him doing the shooting, while shooting was going on.
This leads me to wonder if Cruz was even involved.
Unless she's lying, there is a perp at large, right now, that did shoot children.
I have seen another clip in which another student confirms there was more than one shooter.
If Cruz had anything to do with shooting, he wasn't alone.
Then her response when asked to why she wasn't scared would be "At the time I had no idea it was him (Cruz). Instead she cited the reason as second active shooter. Follow along buddy.
And a key phrase I saw him "After the fact".