"Betas Aside" is a companion novel in The Stars of the Pack series and it focuses on Ray's little sister, Marisa Halley. The 17-year-old beta pretty much takes over running when she's allowed to leave her birth pack and join her big brothers. Marisa loves her family, including her brother and his children, but she has some regrets that make it a little hard for her to fully accept her place in the pack.
With her joins another beta, Irina, who's Iesu's older cousin and, at 30, definitely knows she will never present. She's happy with that but it does mean she's not so certain her connection with her family--mostly still in Ray's original pack--and the newly formed Halley Pack is strong enough to keep her from going back to Romania. Her fear that if she returns she won't be able to leave means that she's never even visited her native land in ten years.
"Betas Aside" is a lesbian or f/f romance and can be read independently BUT it also contains spoilers for the rest of the series.