I need help with an STD question?

Ok so I went to the gyno with my cuzzin a few days ago and today she got her results saying she got chlamydia she got meds to be treated for it but my question is she is worried she can't get preg cuz of this I'm not sure how long she had it neither is she cuz he ex cheated a lot but me and her read that it can cause infertility by blocking the fallopian tubes but I also read this is known as sumthing called PID. Does the chlamydia itseld cause infertility or is it when it turns to the pid I asked abourt