Mona is Elaine Belloc's best friend and was murdered by an assailant whose identity was not learned for some time, and as such was left on Earth as a ghost until she was finally granted death.

Mona Doyle

Mona is Elaine Belloc's best friend and was murdered by an assailant whose identity was not learned for some time, and as such was left on Earth as a ghost until she was finally granted death.

All data from the awesome folks at Marvel.