tourist visa to usa

My sister have B-1 visa for 10 years. The first time she cam visit me in May for 10 days. Then she went back to Thailand for about 3 months now.

I am going to get married at the end of August and I want her to come to my wedding.

Is it okay if she come back to the country ? I heard that you have to go back to your country at least 6 month.

Thank you.