As such their is no diagnosis of "love addiction" in DSM (diagnostic and statistical manual). However any behaviour which is practised in excess, practised eventhough knowing it's physical or psychological ill effects, leading to trouble in relationships, Giving up important things in your life for addictive behaviour etc can be considered sort of addiction.
Next Steps
Your friend can consult a psychiatrist ( online or offline) for full evaluation and management.
Best of luck.