One of my biggest concerns was- since she is a gaited mare would having shoes with heel/toes hurt her natural gait. She is such a great mare I want to do what ever is in her best interest,, but flat shoes do not work where we ride,, she slips quite a bit and I don't want to take a chance of her getting hurt..
I'm not sure what you mean by a "flat" shoe.
There are ways to increase the traction of a shoe, but they are mostly used for "sport" horses (like Eventers and Hunt horses who must work on a variety of surfaces over the course of a year). There are other ways to better traction on paved surfaces. Anytime you use these techniques, however, you must be aware that under some circumstances they can put significant stress on the hoof and/or lower leg.
Again, if the trim is to anatomical correctness you'll get her "native" gait. That may or may not be the gait you want or a gait that will win any prizes. A correctly applied shoe will not change that.