My girlfreind got a sti?

Well my girlfriend just recently found out she has a yeast infection and a veneral diesease. But i thought they were the same thing. Guess not. But i don't no how she got it. We havnet had sex. except 1 time i rubd my penis agaist her cliq once. but ima virgin. how could i have gave her sumtn? she's also a virgin. I wana get testd and am going to but i just don't understand how this situation has happnd. I have 0 symtons. N never had any. how could she have gotton something?