Gwen has long wavy blond hair and a dainty, "china doll" appearance. Her eyes are big and brown, intense and intelligent. Anita considers her a compelling person from the first glance, even discounting her aura of lycanthropic power.
History within series
After Sylvie is tortured and gang-raped and brought to the lycanthropes' makeshift emergency room for treatment, Jason calls Gwen in. Anita hears of and meets Gwen for the first time at Sylvie's bedside, holding her hand, although the relationship clearly isn't a new one. Gwen compels Sylvie to tell Anita about the wereleopards refusing to participate in the rape and torture at their own peril, even if they have done so before and Sylvie hates them all for it -- enough that they are only alive because Richard has forbidden her from killing them, and enough that she didn't say anything about their plight sooner, wanting them to suffer. Gwen manages to talk Sylvie around to revealing Anita the leopards' expectations of being saved, and helps to explain some wereleopard terminology and customs to Anita. Gwen tells Anita not to be foolish about her quest to save the leopards, and argues with her when she declares fights of succession within the pack forbidden for now, but promises to pass the word to the pack when Anita doesn't budge. Before Anita leaves, Gwen compels Sylvia to reveal to Anita the other main perpetrator in the rape, wanting to make sure the people who hurt her girlfriend would die for their crimes. Gwen wants Anita's promise for that, but she has already given it.
After Anita gets the leopards out and back to her house, Gwen takes one of them, Vivian (who was also raped and tortured by the Council representatives), to see Sylvie, who is also recovering there. Anita comments that it's nice to have a trained therapist in the house.
A bit later there's an attempt at Anita's life, and afterwards Gwen gets back and snipes with Jamil, calling him a homophobic bastard. She reveals to Anita that he used to be so persistent at hitting at Gwen that Sylvie kicked his ass. Gwen, Jamil, Anita, and Louie discuss the assassination attempt and Richard's leadership and how that differs from Raina and Marcus in good and bad. None of the wolves mourn the loss of their previous leaders.
In this novel Gwen has mysteriously ceased to exist and Sylvie's sexual orientation has done a U-turn since she claims she doesn't do women. This is likely a mistake rather than an indication of a break-up.
Gwen is presumably back in this novel, although she isn't mentioned by name. Regardless, Sylvie again has a female partner who doesn't need a man in her life in any way, and we have not been given any reason to think this partner isn't Gwen.