I think that her Oathsworn choice shouldn't be permanent
If someone uses her in the bot lane, they're obviously going to bind to their support, but in the late game, Nami isn't exactly the person you want to pick up and throw at the enemy team.
But I can also understand that who you choose to be Bound to you should be and feel impactful, not just flippant or irrelevant, so the idea I had was that since you gain you first Spear free, ever Spear after that would cost an additional 1000 gold (Free, 1000, 2000, ect)
You /could/ change who your bound to if you want, but there would be that increasing penalty for doing so
I also noticed that her W scout would fail to cast if you were attacking something, since Kalista cannot cancel her attack animation
While in lane farming, I would throw out a sentinel to check the river, but the ability would 'channel' and then fail unless I pointedly stopped acting and re-cast the ability
it doesn't sound like that big an issue, but that 2-3 seconds of inaction more than enough time for a Leona or Lee Sin to jump onto you
I thought it would be a little QoL change to let her W be able to override her attack animation