Eurus wanted Sherlock to hurt Molly, and hurt himself in the process

 (Sherlock meta by penfairy)

Eurus wanted Sherlock to hurt Molly, and hurt himself in the process, but more importantly that was her way of making him admit he loves Molly. She set up the game so that Sherlock thought he had to make Molly say those words - but when he fulfilled this aim, he lost. He lost, because Eurus’ aim was actually to make Sherlock sincerely say I love you.

Eurus can read people in seconds, and she knew that the only way Molly would ever admit she loved Sherlock was if Sherlock said he loved her first. Molly was always so careful to keep her feelings to herself; she made sure her unrequited crush was her problem and not his; she respected his boundaries and didn’t let it get in the way of their friendship. So of course, only one thing could make her speak up. Molly’s challenge for Sherlock to say it first was initially rooted in fear that this was a game, and she refused to make a fool of herself unless he did. He stumbles out a clumsy I love you, blinks in awe, and says it again, this time truly, sincerely. It is the second I love you, ringing with a note of tragic truth, that makes her whisper it back instead of hanging up.

Think about how Eurus set this up. Think about the fact that the “I love you” is written on Molly’s coffin. If Molly were inside that coffin, as we are meant to imagine her, then those three words would necessarily have been engraved there by someone else. They are not Molly’s words. Those words on Molly’s coffin are FOR Molly - an epitaph, from someone who loves her. Mycroft was wrong. The question to ask was not “who loves you?” but rather “whom do you love?” because if Sherlock did not love this person in return, then where would the emotional context be? Those words are Sherlock’s.

The platonic or romantic argument is another matter, but the point is that Eurus was vivisecting Sherlock here, and she wanted to see HIM come to terms with his love for Molly, and to see him grapple with how much he wants to protect her and how painful it is for him to hurt her in any way. It’s this heady brew of emotions that makes him absolutely lose his mind. He trashes the coffin and screams in agony, because he loves her, because he hurt her, because it is pure torture to be cruel to her or to think of her in that coffin, with “so many words unsaid.” Particularly those words - his words, for her.