Why was she as TV tropes would put it, placed on a bus. It was an excellent show, the proto-angel and she and Nicks chemistry was the best thing about it much better than Nick and what the plump coronor’s name, Natalie ever were.
There is some good info on the characters wiki page.
spoilers
It’s hard to say why she left. A lot of characters drifted in and out of that show. It was only on 3 seasons. I’ve wondered why the cast changed so much.
The shows final ending was so horrific that I haven’t been able to watch the series again. The 3rd season is the most depressing tv show I’ve ever seen.
Not to mention inane. The writers should have been shot …errr… staked.