I don;t like the redscare, but refusing to shake hand with Sanders is going to get played in a lot of places.
She should have sucked it up if even if she was absolutely disgusted with Sander's/
this is assuming that's what happened.
But I agree you should always shake a hand when offered (unless that person didn't wash their hands or you know is very unhygienic).
Even if you have a legit reason (and hating a person's guts maybe one) it always looks bad for the person refusing.
If Warren is pissed that Bernie lied, good for her because she should be pissed, but most people and voters still don't think highly of people (Especially candidates and especially women) that can't set aside emotions or differences for simple things like handshakes.