Can you just twist itself together like a twizzler?
So if it's a 6 foot vine, it would be around 3 feet. I am of course assuming it is the fake bendy vines that Exo-terra/Flukers make.
If you're talking about fake vines that have leaves and stuff, you can cut it yes. Just be smart about where the wire ends up, or you could wrap the wire end with tape.
I would be careful with the wire inside. If you use something to cover the exposed wire that the chameleon can't eat/is safe for it, then you probably can. I would just do what was said above and twist it together or find a way to use the whole thing.