I Had Sex With My Gf On 13th Feb At

I had sex with my gf on 13th Feb at 1:30 pm and condom burst inside her vagina. She has mitral valve replacement surgery 4 month ago and she was taking anti-coagulants regularly. She had her period starting on 2nd Feb of this month. What is the possibility of getting pregnant. Also due to her anti-coagulant therapy I can not give her any contraceptive pill. Plz help me I am very afraid. She has her period from 2nd to 7th Feb I think. We still not completed 24 hour after sex