Is streptococcus in the vagina dangerous and how long does it take to cure it?

Streptococci is the name for a whole group of different microbes. I suppose you may be referring to group B streptococcus (Streptococcus agalactiae). For healthy women, it is generally not a threat - quite often it is part of the vaginal microflora. However, it can be dangerous for pregnant women and newborns. For this reason, patients between 35 and 37 weeks of pregnancy are tested to see if they are carriers of this bacterium. If so, an antibiotic is given at the time of childbirth. I enclose additional information: https://www.gdziepolek.pl/artykuly/fakty-i-mity-o-antybiotykach