As people said before groundwork and just hanging out with your horse are great ways to build trust. Also you could get a tarp or blanket or other "spooky" objects and play around with them. It helps the horse to be more relaxed around you, build her self esteem and get her to think "if this human is with me I am safe, even if there are spooky things lying around"
Spend somemore time doing ground work with her or just hang out together. If you googled Liberty Work with Horses, I do it with my horses and I’ve noticed a massive change in trust. I hope this helps! 😊
When I first got my mare I would just go out and hang out with her in her pasture (her space) so we could just be together. That way it wasn't always if you see me it means work. Idk it was just a small kind of building block to get her used to me