Could she be pregnant?

my girlfriend and i had sex, were been together for some time and shes been on the birth control pill for over a month. i was wearing a condom and i pulled out BEFORE i finished but when i pulled out i realized it had broken. it must have broken with in the past minute or 2 minutes. , do you think theres possible pregnancy? should i be concerned enough for plan b? and if plan b is taken when you dont actually need it could it harm her? thanks