Thanks for the comment on My Sanity! :D I'm really glad you enjoyed it and that you'll be adding it to your reading list and continuing to read it :)
Well, Riella is just depressed. I think it's called clinical depression? I'm not sure hahaha. It's not really a mental disorder like bipolar or anything.
Her depression is a result of a horrible incident that happened to her in her life. ;P It's still a mystery though, I'll be telling it later on :)