Coping with Clara

Charlotte can see her sister. Now you may think that's normal but it's not. Her sister died just under a year ago while saving her from a lorry. During the time after her sister's death, Charlotte went off the rails until Clara came and put her life back on track. Charlotte is the only one that can see Clara.
Clara loved ballet. Charlotte begins seeing how sad Clara is and offers her an amazing chance. Clara can live through Charlotte and dance ballet just like before. But soon Clara loves having a body too much and begins to overpower Charlotte. Soon, Clara can fully take over Charlotte's body, only leaving her in her mind, having no control over her actions. Charlotte is being lost, could it be forever? And could Charlotte's new love interest realise what is happening?