Gwen actually had an important role in betraying Team Angel to help Vamp!Gunn, but got a bit of redemption by sacrificing herself in order to save... Angel? Can't remember exactly, but save whoever from W&H retribution. She came back in the reset along with Connor, who she was actually in a relationship with.
Illyria also got released from Fred's "shell" by Vamp!Gunn towards the end of the arc and went on a rampage. Team Angel killed her/him/it, and then the reset happened.