"He vomited when he saw through Dolohov what Quirrell was doing to her, Ron.  Snape.  In front of several people.  He was actually shaking.  He cried when we found her.  Actual tears.  Like it or not he is in love with her, just like she is with him.  Losing him – losing any of them – will destroy her.  Don’t you think she’s been through enough lately without you adding to it?"