Hiya, I'm not sure where you're located, but altering the strap is not difficult on this bag from what I can see. You'd need to find somebody to add extra holes and perhaps cut a bit off of the end so that you don't have a tail flapping around back there
Cobblers in my area wouldn't charge more than around 30 euros for that.
I've never tried on this style in real life, but from what I can see of the dimensions (24.5cm x 17cm), it wouldn't be too large to wear as a shoulder bag for a small framed person. I'm a bit taller than you at 157cm, but very slightly built, and I've several bags in this size range that don't look outlandishly big. Maybe you need some time to get used to the size if you're accustomed to carrying smaller bags?
I sold a Neo with an altered strap a while ago at the same price that equivalent Neos with 'stock' straps sell for in my country. The person who bought it was thrilled, she was more or less the same height as
@ziagouel and happy to not have to go to the cobbler herself. If it's professionally done, it does limit your clientele to people who are the same size as you, but doesn't impact resale value too much