Well 10000% she is red based. No buckskin, no bay dun.
I suspect maybe champagne too (not bothering with pedigree lol) I sort of see mottled skin and stuff but would like better pics.
So she is chestnut with maybe a dun (unlikely imo) or champagne gene. I love her tail.
Confo- she is cute, she needs a diet and good farrier yesterday!!..Aside from the fact that she looks like a very cute cow and I suspect a lot of my complaints are due to the weight, she is definitely standing under herself (farrier?) don't like her front legs, but it may be due to the way she's standing, her back legs appear sickle hocked and maybe slightly cowhocked, maybe also a little too close (would need to see a pic from the back)
I think with a good diet and a good farrier she would be stunning!! I really like her, and she's not perfect but no horse is, and I don't love her legs but there isn't anything major.. it really depends on what you are looking for and as I said I think she'd be a different horse with a little tlc.
I would post a picture in the critique section too, you'll get better responses.