Wife Pregnant Before Marriage

i am Hindu man of 31. i had inter-caste marriage with Muslim lady of 29 i met on matrimonial website. I met her only few times, but i like her very much and decide to marry her. because of different religion, we had marriage in court. i did not notice early on becos she always put on very loose cloths, but after marriage & when we are going to consumate, i find out her belly is looking tight & swollen. i ask her about it & she told me she had female problem few years back, becos of that her belly is looking like that. i went away for some work after that, and when i return i see her belly is more swollen. so i make her come with me to doctor, who did ultrasound and told me she is 7 month pregnant. but i met her first time only 4-5 months ago. she now tells me she does not who father of child is, so she decide to quickly marry someone as that man can give name to her child. she tells she was going to tell me and wants me to accept her child as mine. but how i can i accept that child. i also feel cheated by her so much. i am not living with her now & want to leave her becos of all of this. but she is threatening, telling me she will tell that child is mine if I think to divorce her, that we have relations before & being lady all will believe only her. but i don't want anything to do with her. what to do now. my english is not good, but please understand my problem & give me your advice.