We are just back from Universal and also went last year, and I have a timid 8 year old. She loves Hippogriff and wouldn't go near FJ. Hippogriff is not as intense as Big Thunder Mountain (she has ridden BTMRR once, but I couldn't get her off Hippogriff). Hippogriff is faster and longer than Goofy's Barnstormer at WDW, which I'm guessing is similar to the Casey Jr.
She was scared to try Spiderman since she rode it at 3 1/2 and got traumatized. But she liked it this time. No way could she have handled FJ, but that is partly because of the intensity of the things that jump out as much as the ride motion. FJ makes me sick to my stomach - I only ride it once per trip.
Another thing about FJ is that you can't really see the person sitting in the seat next to you, so even if you are next to her, she will feel like she is by herself.