does washing off sperm with soap and water kill it?

So a while ago my gf and I were mutually masturbating. She asked me to *** on her butt cheek and I did. After that we immediately showered with soap and water. I was wondering if washing off the semen would render semen ineffective because I'm having a scare that somehow some of the *** might have been washed down to her vagina and cause pregnancy. No penetrative sex involved at all. Also, she got her period a day after so I'm assuming this means she wasn't fertile at the time? Thanks.