After 1st session of laser treatment (Brazilian) I started bleeding vaginally. If this has happened to others, what is going on?

I am not aware of any medical reason that a patient would have vaginal bleeding after laser hair removal to the vaginal area.

I agree, this is not a problem described as a possible side effects of laser treatment. But what is most important is to check a pregnancy test and if you have an intrauterine device and have not reported it to the treating provider, then you should have an appointment to check for any gynecologic issues. And even if you don't have the above problems, still see your doctor and may be have a pelvic ultrasound done as you will need to continue with your hair removal treatments and want to make sure you don't have any organic issues going on. Best luck!