Given she was upset that Tim kept it from his mom, I’d be surprised if her parents don’t know she’s with Tim. But she did say “someone” on purpose. It was a reaction to how he minimised their relationship to “dating”. She was stressing how bare minimum it is to tell your parents.
"I don't talk to my parents at all but I dropped them a line when I moved in with...someone."
S9 needs to explore this!! Lucy doesn't talk to her parents & her wording was specific. Would they not be happy bc he was her T.O? Bc he broke up with her? Bc he's divorced/bit older?