While I sympathize with the family, when my friends and I were young adults, we didn't exactly make a habit of sharing the truth and nothing but the truth with the homefolks.
This was true for me. The family knew only what I decided to tell them. I think they prefered it that way anyhow. No need to dump every detail on the parents and get them all worried.
not to mention that it just seems bizarre that a woman would kill another for too many other reasons that an affair gone wrong- she coulda been killed i suppose for hitting on a boyfriend of the other woman, but it seems like others woudl have picked up on that- the fact that she was shot multiple times seems to indicate rage- maybe there is another explanation, but seems like a lover’s rage might be the answer- she may have been embarrassed about being a lesbian and not told her parents and friends like you suggest- perhaps fearing rejection by her family- but who knows- the woman who shot her knows, and isn’t talking i guess-