Well, that's one way to get rid of repression. Anna has long been attracted to Mompellion, and with Elinor dead, she can no longer hold back the tide of her feelings. It ends up being a mixed bag. On the one hand, she feels incredible after having removed the yoke of sexual repression. On the other, she feels shame for betraying her recently deceased friend.

This is a yuge revelation. Anna has always seen Elinor and Michael as the perfect couple, so she's shocked when Michael reveals that they never ever had sex. This was his way of punishing Elinor for her prior sexual activity. In this light, the second sentence in the passage is particularly disturbing: Michael made Elinor love him in order to cause her pain. Yikes. Talk about repressed.