she stay in a pasture, not sure i have a way to put her on a shelter or a fan. /: i'm not sure about the muzzle beacuse i bought her with it and the owner's said that she was scratching herself - but it can be only a normal reaction as any horse. i work at that stable every day so i can spray her once a day and keep an eye on the fly sheet if a decide to buy one. (right now i don't have alot of money to afford it.)
her coat is taking care of, every weekend i go with her for a big ride and when we come back i make her a big good shower to help make a relief from the ichy and the heat.
she also Scratched almost all of her mane. there's a way to stop her from doing it?
It is crucial for any animal to have some form of shelter, even if it is natural shelter (say trees). That is an absolute must and not negotiable.
Some type of barn or something you could shut her in to and put a fan on would be ideal but I get it's not always doable but I would make her a shed or something at least.
A horse scratching itself with teeth is ABSOLUTELY normal and OK. Now if she's doing is constantly she is clearly bothered by something (your job to find out what) and if she's actually hurting herself (biting, scratching with teeth until she bleeds, etc) then something is wrong and not only is it your job to find out what but it's your job to stop the self-harm. I have NEVER known a horse to do the latter and would only imagine one doing so that is seriously ill (say rabies). Even my pony with severe sweet itch who does self harm itching does so by rubbing and NEVER bites herself more than on occasional itch as is normal. I really bet if you take off that contraption she would be just fine and a lot happier. Obviously the bugs are still an issue but can you imagine having an itch and having a hot uncomfortable contraption rigged up so you can't itch it? I would get rid of that and see what happens, I bet nothing too exciting! (That's not a grazing muzzle btw, though it will stop her from biting herself/itching!)
Now obviously she's miserable from the bugs/heat and that still needs to be addressed. She is scratching her mane because of that (same with the itching teeth) you need to address the bug issue. I know it's easier said than done!!
Her coat looks rough because she scratches a lot.
What is "hot" to you? Is it humid?
It's great you are out their daily. I would give her a hose down when you are out and fly spray after. I don't know how long you are there but it may be worthwhile to do that twice (when you come/before you leave)
If there are people around maybe someone could help you with this?
As I said I have a horse with sweet itch so I understand your dilemma!
Get her some kind of shelter, inside with a fan during the day would be ideal. Hose down as needed for heat/sweat (sweat attracts the flies remember) and always apply fly spray after, apply fly spray at LEAST every morning. I would recommend a full fly set up (I recommend a fly mask WITH ears as well as a fly sheet with a neck, maybe boots if she stomps a lot but she is probably fine). Remember to get something that won't make her hotter as much as possible and remember that sweat=flies so lots of cleaning. Any trouble spots should get extra attention. I would definitely take the muzzle off and see what happens, in fact it may be making things worse. Having a vet check her over would be good.
Do you have any more pictures? Her coat looks long and she may benefit from being clipped (after you get the fly sheet and start your action plan). My mare has a rough coat just from the trauma of spending every summer rubbing none stop, it doesn't grow back as nicely as it used to.