She showers immediately upon coming home after being out with friends

what does it mean when a woman heads for the shower after being out with friends? Everytime my SO comes home after being out with a best friend, she makes a beeline straight for the shower. He lives overseas (and is also an ex BF) so it's once, maybe twice a year. She returns late, late at night, like 2 to 5 a.m. The first two times, we had knock out sex after her shower. Since then, she comes to bed and turns her back on me. I've met the guy a few times, seems nice and respectful enough. Not sure thus matters, but she masturbates with dildos virtually every shower and and positively during these late nights out