I don't fucking get it /bant/ how did this happen?

I made out with my qt light brown gf this sunday then yesterday found out I had strep throat after a quick culture at a clinic. So I did the responsible thing and told her, she went to get a strep test today and it came out negative

HOW!? How can I stick my strep infected tongue down her throat swapping saliva like crazy without her getting it at all? I've gotten it from talking to people, from touching the same chip bowl! HOW IS THIS POSSIBLE?!