My girlfriend is refusing to take birth control pill, because she's scared, can i put this pill in the food or crush it and put it with liquids ?

Terrible idea: It's a terrible idea to give someone medicine without their knowing. Why don't you use condoms? A doctor can properly explain the health benefits (there are many) of birth control and the risks (blood clot is biggest). But as they boyfriend you have to respect her decision if she says she doesn't want to take. Sounds like relationship needs some counseling? Consider speaking with therapist.