Plan B
Morning after pill, get to the drug store and get this! Its like birth control but it kills off anything that may happen! Also you have to use it right after sex until the 48 hour mark. If she is past this buy a pregnancy test and hope for the best!
Be more careful next time use condoms if you aren't ready to make babies lol!
Explain to your girlfriend its important to you that she listens even though it is hard when you are enjoying yourself and in another world.
I wish you luck!