When I look at the soles, the white line (which is dark pink) is right up to the edge of the hoof at the toe. I don't think she could trim off anymore than she has without actually going into the white line.
Yep, without sole pics, not sure, but suspect that you may have a little way to go, but ensuring you keep the toes back at least to the white line with a strong bevel would be good - while you don't want to invade the actual sole, you can at least make the bevel a lot steeper, and you may be able to go into the 'white line', to keep everything outside relieved. But it depends & I haven't seen the foot properly...
My horse's heels seemed painful to me. .... I am want her to lose 100lbs and also build up some muscle. She was reluctant to walk much without the boots. With the boots she is much more willing. So, now I can increase her excersize
That's great... not the sore heels but that you've got boots & found they're working for her & *gentle exercise will be good for her *so long as she's comfortable & not forced. Yes, with heels - or lack of - like that, would expect her to be sore on them - & inside them. I think heel support is a good idea, but instead of jacking the whole foot up at the back, I would be providing a bit of gentle support *under the frog*. Heels are already weak, so softish & thinnish best, for now at least, and being only under the frog, will give the heels some slight relief, to hopefully allow them to start growing down. You can duct tape foam 'frog supports' to her feet before booting, or glue them in the boots.