Your emotions are your emotions. What we construe as moral or immoral/ good or bad can differ by person. Just don't be an ignorant prick and go holding picket signs outside of her funeral saying God wanted her to die... like some ignorant assholes do.

None of us have been in your situation with her. However, if she was just a loud bitch, and didn't harm you physically or emotionally... I'd say feeling happy about it would be sorta wrong.