Oh for the love of god stop freaking out about Camille's ultimate.

Her ultimate prevents her target from escaping. Okay. So what?

It doesn't prevent anyone else from entering or exiting. It only knocks back the target's allies briefly at the start once. If Camille dies or she leaves the circle herself, the zone goes down and the target is free to leave. There's no other additional effects besides buffing Camille's autos. No stun threat like Veigar's cage. No massive instantaneous damage/DoT like Jarvan's ultimate. No delayed nuke like Fizz's ultimate.

So just kill her. Or get your team to come back and protect you or just harrass her the hell out of her own cage.

If anything at all was a potential problem, it would be a potential triple auto reset (auto-Q-Q2-Hydra), although I'm not sure how long the delay is on the Q, which might prevent it. Otherwise, she seems fairly balanced, and unless her numbers are through the roof (cough), I think she'll be fine.

As for numbers issue, that can all be tweaked. Even her mobility (how often she can jump/dash around) can all just be tweaked by CD/mana cost nerfs. The kit itself in concept looks fine.