You're fine, hun. Calm down. Sperm do swim, but not through air

More than likely, your penis was closer to her urethra than her vagina while the rubbing occurred. It's very unlikely to get pregnant by precum, even when it is from a penis fully penetrating a woman. Also, there is only about 5 days every month that each woman could get pregnant. The chances your little drop of sperm got through her shorts and underwear, into her vagina, into her cervix, and happened to fertilize a waiting egg? Next to none. She's not pregnant
It is alllwaays best when there is any contact at all occurring to wear a condom. If she has had any sexual contact at all (giving or receiving oral sex, included) then even though she is a virgin, she could have contracted an std. If you've ever had any kind of contact or any sex at all without a condom, you are at risk as well. Some people could even have HIV or a few others STD's that they contracted from their mother during prenatal development or vaginal birth. Also, obviously, condoms protect against unwanted pregnancies. If your girlfriend and you are going to continue your sex life and perhaps even further it in the future, I suggest using some sort of barrier method (condoms) of birth control.
If she is 16, you better be sure her parents consent to your relationship before you consider taking it to the next level. If you love the girl, then respect her enough to wait until she is a little older before having sex with her. 16 is pretty young.