How Do I Tell Her That I Don't Want To Marry Her ?? -

I met this girl in 2009 when i was in Nigeria, she's really a sweet girl and was 23 at the time.
She's really lovely, a good cook and a ride or die, she will do anything i tell her but she had a problem, she can't say no to s*x.
I wanted to marry her but i found out how unfaithful she was, she can fu*k anything, she even slept with  two of my friends but i didn't wanna hurt her by telling her i knew she fu*ked my guys.

I was lucky to get out of the relationship alive because she's the kind of girl that would kill you and then commit suicide if you ever tell her you want a break up.
I got the opportunity to permanently move to America, one month before i traveled, she fu*ked 2 of my cousins. It didn't bother me because i knew it's over because she won't see me again for the rest of her life.
We've been talking on Skype, phone,Facebook and WhatsApp since i got here and i still tell her i still love her and want to marry her but on some real shiit, i don't wanna marry her even if you put a gun to my head.

She recently was talking of sending money so i would come down next month and marry her, her dad is filthy rich, how do i tell her i don't want to marry her.

She can kill herself if i ever tell her