yea, it's indeed challenging to make ice bridge in this manner. Sadly, this is the quickest way for her as compared to doing her full attack sequence for a longer ice bridge.
Don't worry, she is there to supervise the action scene. That's how most of the behind the scenes, ends up with Charlotte swimming and Furina standing on water to correct her posture.
I feel like you could add the name charlotte in front of any word, and it could be the name of a significant book or movie. Especially this title rn 🤣 "Charlotte's Bridge" in theatres February 28th
Such a shame what they did to her, she should have the same cryo app in NA as wrio to be able to ice bridge more smoothly, it didn't even had to be as wide as his but at least as consistent