Thank you so much S.Tighe! I took it in today to get the corner repaired. He suggested just splicing the small area instead of replacing the whole piping (to keep it as original as possible). I went with his suggestion I hope I made the right decision.
Sounds like the right move... Worst case, you decide you don't like it and have him replace the whole thing, but if he suggested just that bit it sounds like someone who knows what he's doing. I had the same suggestion from my leather guy, who is the repair shop the local Balenciaga boutique sends out to... He's been doing leather repair for 3 decades (!) and sees lots of balenciagas. My corner wasn't totally worn thru though, just "scabby" and I was able to fix it up DIY. Post pics when u get her back! I'm a total sucker for black city bags, I'd have one from every year if I could....