Solo female travel to Iran is exactly the same as male travels to Iran. Iran is quite safe especially for women, just stick to the general safety guidelines. Iran is even safer than many other countries. People are so hospitable and kind to the tourists. They are helpful as well, so whenever you need help, be sure that there is someone who is eager to help. Violence against foreign women is almost unheard of in Iran.
Maybe one of the main differences to other countries you’d traveled before, is Iranian dress code and hijab, and this is the biggest concern for female travelers to Iran. As an Islamic country, Iran has its own rules for dressing in public. In general, the best tip is to see what locals of the same sex and similar age to you are wearing, in everyday public life. Then ‘do as the Romans do’!
As a woman, you should cover the hair with headscarves. This headscarf accompanies you all time you’re in the country except in hotel’s room. If your headscarf falls (which happens often!) don’t worry and quickly put it back on again. It’s not so serious point, but just pay attention at all times. The other one is " Manto " that is your body cover. Wear somehow loose-fitting tops and three-quarter length sleeves are acceptable. Read more about Iran dress code