What a dynamic episode, and all the conflicting emotions were well expressed - I felt her vacillate between her old lover and her new.
Your descriptions were very vivid also - great work.
I think she should come clean to Enzo, protect him from the double cross if it is him she loves the most.
If she buys Alec a little more time he can tell her why made the choices he did,. Maybe his reasons to want Enzo stopped will be convincing enough to trump Serena's love for the Mafia boss. She might decide E has to go behind bars for the greater good ... although so far she seems accepting and complicit in his gang lord ways. And her love for him seems to conquer other concerns. Sex for old times sake can be something you wonder about ... do once & realise you've moved on.