I think she committed suicide but how?

she shot a gun into her head...

In the words of Jinny, she "blew her brains out". We don't know why, but we'll probably find out later in season 2! :D

For the whole story watch the episode "Intervention"

Yeah, she commited suicide by shooting herself, like the others said. I think that also explains some of Jinny's 'issues'
Heck, the Exstead's 'issues' for that matter...