I have a friend who had unprotected with a person who has , is there a chance sho wont get it?

When I contracted it, I started having symptoms about 2 days after the first time I slept with my boyfriend at the time, who I did not know had it. Dont know if that helps. However, I have had boyfriends who slept with me without protection, knowing that I had it. I have never given it to anyone in 13 years, so, to answer your question, yes, there is a chance she could get it from one time sleeping with him...it happened to me!