I have! Just drop it into an LV store, they’ll give you a rough quote and then it goes off to France for repair. Can take around 3-4 months to come back though. For just the shoulder strap you’re probably looking at £200-£300 (based purely on what I had repaired on one of mine).
Worth noting though that if the repairs your stepmum had done weren‘t done by LV I don’t think they’re keen on touching the bags after that, but there are other places that would work on it.
As
@RR20 has just said, you could always sell it on (if it’s not sentimental of course!) - the Noe is very popular in the resale market.
Edited to add if you’re not near an LV store you can email pictures then post the bag to a store and they will quote for the repair. If you’re not happy they send it back to you.