[Spoilers Vol 4, Ep 1]

Emerald is not okay with what's going on.

While she is still fiercely loyal to--and possibly in love with--Cinder (note her shoving Mercury out of the way to simply stand next to Cinder when summoned), she's starting to crack under the strain. We already saw her hesitancy during the fall of Beacon ("It's almost sad..."), and the terrifying Deathly Hallows style conference with team WTCH in Salem-land (hence forth known as Massachusetts) isn't exactly helping her calm.  Even Cinder's desire for vengeance against Ruby makes her take pause. Ruby may have annoyed her ("How can they be so happy all the time?!"), but she probably never wanted her dead.

Emerald's semblance is still absolutely terrifying; heavy use of it and a complete fall to the dark side would probably earn her one of the two mystery seats at Salem's table. However, if she's faced with possibly witnessing Ruby's violent and brutal demise... as previously speculated she is almost certainly not going to be able to stand idly by.