False postive from taking xanax !

So i read that xanax can cause a false postive . I never heard this before .so as i am a poas freak i had a extra test and my sister actually took 1 xanax yesterday night . So i asked her if she would lol.and omg SHE GOT A FAINT POSITIVE!! the picture does no justice in person its a faint pink line no squinters .it looked like mine at 11 dpo