Oh no! That’s very frustrating!
If it was me, I’d go for the easiest (sorry, more straightforward) method first and try and find a piece of material that just matches that end bit and replace that. Knowing my luck though, I’d probably end up having to rebind the whole neckline, gathers and all!
Oh no! I think making a little more binding is an excellent idea. The blouse is so lovely it could be worth taking off the torn binding and splicing in another piece of the same fabric!
If you have more fabric to make binding I would unpick just a bit and do a join and reattache the tie. I am thinking of a join that you would add as you would do if you were binding a quilt block or when making piping. Not sure if that makes sense or not.