Well, none of the options as I see them at the moment are particularly compelling to me, and I'm falling asleep over here and thus not feeling sharp enough to make judgment calls. I'll outline what options I see, and maybe someone can weigh in with something else (or just forge ahead after I'm gone, either way). I'd love to see someone mention something more creative than any of these, but it's not coming to me at the moment, at least.
A) Throw the trident in front of Tewi: I mentioned my reservations about this earlier. Simply put, I don't hold out much hope of this actually causing her to stumble, nor do we really seem to have time or positioning to use it to force her into someone/something else
B) Just shoot Tewi: We tried shooting in front of her, and she managed to roll through a wall with minimal damage. Theoretically, it should probably be harder to dodge fire from behind, but I wouldn't put it past her. Even if we hit her, she might be able to take a few shots without it slowing her enough to keep her from getting away.
C) Throw the trident in front of Tewi while also firing danmaku to either attempt to drive her off of trivially avoiding it, or to simply reduce her co-ordination in avoiding it. While this would be nice in theory, I suspect that the sloppiness that doing these two things at once will cause (as inquired about below) stands a high chance of making the overall attempt ineffective.
All things being equal, I think I'm most inclined towards B. I feel it's more likely to slow her down at least a little than A is (and allows us to keep the trident in hand for following actions). I don't really think it's ENOUGH, but nothing I can come up with feels like it has a high chance of keeping her from making it into the woods (which is why I haven't just picked one and gone with it, yet).