About pregnancy. It would be doctor?

Helo Doctor, I Hope you only can help my sister. She had sex with her partner before 2 weeks(May 17th, 2018,Evening)without intercourse or penetration. She is not sure that his sperms went inside or not. She even not sure that she is pregnant or not. She don't want to get pregnant right now. She is worrying alot about it. Last time her periods occurred at May 4th,2018. Usually her periods occurs at 2 days before her previous period. So this time her period have to come on June 2nd,2018(Because her previous period at May 4th,2018). But Today(May31,2018) she is bleeding. She is confusing that its a normal menstrual or implantation bleeding. Because she is bleeding 2 days before of her expecting period. What it would be doctor? Please help my sister...