iserith
Magic Wordsmith
Thing #1 is not really a DM thing, more a role-play and intra-party dynamic. The player decided her character was frightened when the fight started and chose to roll all attacks etc at disadvantage. The rest of the group was understandably a bit shocked as I think this development was not sufficiently telegraphed. The character had seemed quite tough until that point.
That's weird. You can be frightened without being Frightened and I don't see how that's a player's role to decide. I could see the DM mandating it for reasons or offering it as an option to the player in exchange for Inspiration (not a great trade, but better than nothing). But the player deciding? Nah.