I doubt very much that your girlfriend would fall pregnant from this, if you are washing your hand properly and with anti bacterial soap then there shouldnt be a chance of her gettin pregnant however if your just giving them a quick wipe then yes theres always that chance that she could get prgnant!! .....she most likely probably wont though!
Noooo dont take the plan b thats just a waste i dont thing there any chance of her becoming pregnant inless god sent her a gived.
You can try Plan B, but I doubt it would do anything. It prevents ovulation, nothing more. And can cause much more stress than it can be worth. It's known to cause spotting, early/late periods and missed periods. Your chances of pregnancy are very slim, but they are still slight. Try not to worry about it, because stress alone can delay a period leading to more stress.