my girlfriend recently ended a abusive relationship

My girlfriend (25) and I (29) have been seeing each other for over a month now. We both work in the same building and we have been eating lunch together for about 3 1/2 years so we are really close friends. The entire time I have known her she has been engaged to this guy that to this day I have never met so I never advanced on her until recently. We started flirting with each other and its become a relationship of some kind. About 2 weeks ago she came to work head to toe in bruises, her fiance tried to strangle her (aparently he has been abusing her for almost a year and is a drunk) and she moved in with his mom who owns the apartment complex and has been there since. This relationship between us has grown pretty strong at a intense speed, she assures me she wants to be with me and that I am not a rebound (we even sleep together on breaks only after the breakup) but it feels off. I feel bad because I push her to be with me for real and hangout outside of work and let me dote on her but she has not told anyone in her family, won’t change her Facebook statues or even take the ring off saying she is still processing what’s happened.
It feels incredibly selfish on my end to be upset that she is dating me while still wearing someone else’s ring and not being able to take her on dates. (She doesn’t want his mom to know she is dating already and she does not have a car). I feel like I am being unreasonable and wanting to much to fast. I can’t help but wonder if the reason the breakup is a secret to everyone including friends is because they are still together and I’m just her side piece. I can’t wrap my head around why someone would continue to wear the engagement ring of someone who tried to kill them, she wont press charges.
Any advice would be appreciated thank you