Using kissing to transfer life energy is cheap and over used. Plus stealing life energy is way out of character for an angel. That's a vampire or a succubus's shtick.
That said it gets massive points because the angel/Alise was so cute. I could have done without the sexually charged make out... I mean energy stealing scene on the bed. The author couldn't seem to make there mind on whether Alise was the child she looked like, or an useless adult character trapped in a child's body.