It’s really difficult to say, I’d suggest you wash her private parts with saline (human eye wash will do), gently pat it dry and apply an antibiotic ointment. I have no idea what you can get in Iran, but neosporin and fucidin are both rabbit safe.
Then try to stop her from licking the area by putting an E-collar or a make-shift e-collar on her. See if it gets better, if it isn’t it’s sth deeper and she might need systemic antibiotics. Do you see any sores, scabs?
Another suggestion is intestinal parasites which may cause intense itching around the anal area (which is very close to the lady-parts, of course). Rabbits housed outdoors or rabbits that get fresh forage like fresh grass etc can get intestinal worms like pinworms etc.
How is she housed? Rabbits should be housed in dry environments and have a separate place where they go to the bathroom. If she sits in her pee she can get urine scald or hutch burn, which means the corrosive components of her urine is hurting her skin, causing irritation and itch, which, if left untreated, will progress into sores.
Do you know what caused the death of your other 3 rabbits?