IME traditional harnesses are much easier for dogs to slip out of vs well fitted collars. You may need to fit the collar to the top of her neck, or get a limited slip or martingale collar which allows it to sit comfortably at the base of her neck but snugly at the top so she can't slip out. If she only slips her collar when on a leash, I would use a flat collar for her tags (fitted normally) and a martingale collar for walking. That would eliminate the harness rubbing issues, the collar slipping issues, and the potential safety issues of leaving a (limited) slip collar on all the time.
If you want to stick with a harness, the ruffwear webmaster harness is generally a good idea for dogs who slip out of harnesses, as it has a third strap that fits near the end of/just behind the ribcage which can limit a dog's ability to back out. Some harnesses, like the freedom no pull harness, have a martingale action on the chest strap which might make it harder to slip out of- but I've never tested it. Can't say whether either would cause raw spots, but I can say that I don't prefer harnesses with a strap around the shoulders/chest (no pull/front clip) for longer exercise periods because they can interfere with shoulder movement and limit the dog's natural stride, so I personally wouldn't use one with that design on hikes unless I needed that specific no pull action.
I feel like collar slipping can become something of a habit/training issue. My childhood dog was a master collar slipper (you would be walking along, then feel the tiniest tug and look down to find her naked, collar dangling from the end of the leash), and once she went a period of time in an unslippable collar (martingale) and got admonished a few times for trying, she was generally fine in anything, though I still used the martingale for walking most of the time to avoid any risk of escape. For times when I didn't necessarily want the martingale action, but still wanted the no slip protection, I would put the martingale or slip collar at the base of her neck, with a flat collar above that, and hook the leash to both. That way, only the flat collar was in play, unless she started to pull it over her head, in which case the martingale would tighten.
If you want to stick with a harness, the ruffwear webmaster harness is generally a good idea for dogs who slip out of harnesses, as it has a third strap that fits near the end of/just behind the ribcage which can limit a dog's ability to back out. Some harnesses, like the freedom no pull harness, have a martingale action on the chest strap which might make it harder to slip out of- but I've never tested it. Can't say whether either would cause raw spots, but I can say that I don't prefer harnesses with a strap around the shoulders/chest (no pull/front clip) for longer exercise periods because they can interfere with shoulder movement and limit the dog's natural stride, so I personally wouldn't use one with that design on hikes unless I needed that specific no pull action.
I feel like collar slipping can become something of a habit/training issue. My childhood dog was a master collar slipper (you would be walking along, then feel the tiniest tug and look down to find her naked, collar dangling from the end of the leash), and once she went a period of time in an unslippable collar (martingale) and got admonished a few times for trying, she was generally fine in anything, though I still used the martingale for walking most of the time to avoid any risk of escape. For times when I didn't necessarily want the martingale action, but still wanted the no slip protection, I would put the martingale or slip collar at the base of her neck, with a flat collar above that, and hook the leash to both. That way, only the flat collar was in play, unless she started to pull it over her head, in which case the martingale would tighten.
