I have narrow feet as do all my kids. School shoes were a nightmare and we often ended up with European males so might be worth considering those for heels?
ideally if you have an independent shoe shop - they might look like they are for ‘comfortable’ or problem feet, but they will definitely be able to advise on brands to look at.
High street wise - I would look at next, new look and Jones. These have sometimes worked. Both my daughters prom shoes were/are new look (one has prom this year). Both myself and one daughter even got ballet flats from new look when those were in fashion (I’ve never found a pair that fit -anywhere).
i see you’ve looked at Gabor - again they give the impression that the shoes might be ‘comfortable’ which unfortunately often go hand in Hand with wide, but I’ve had shoes and boots from here before.
my ankles used to be super slim, sadly now pretty destroyed due to rheumatoid arthritis but I never found an ankle strap good. The design of the shoe just doesn’t seem to work well on very narrow feet.
Aldo I see your daughter is a 6, like me which is often on display. Ask for a new pair to be brought out rather than trying the display shoe. I drive shop assistants mad by doing this but the display one is always stretched by people with wider feet trying it. Honestly, it can make a huge difference!!