He'd be able to tell if he hurt her, I think.  The problem is finding something that'd hurt her.  Like, I don't think she'd be all that hurt if he did what she did and adopted a child.  I think she would be stunned if she saw him romantically involved with someone else.  It'd really hurt her if he tried to hurt Jonathan or something.  But Jaspin doesn't strike me as the kind of guy who'd hurt someone like that else just to get at Elizabeth.

Of course, betraying her again and trying to get her and her clan killed would do the trick.  But again, not sure Jaspin would try to hurt everyone else just to hurt Elizabeth.  Also, if he did that, I think she'd straight up kill him.  I think she'd have it in her.  

He could tell her he never loved her.  Or perhaps if he were to act like seeing her again meant nothing to him, that'd sting. 

I think that when she sees him again for the first time, one of her first instincts is going to be to touch him.  If he spurns her, if he rejects her whenever she tries to touch him, that'd hurt.