I fell pregnant by a man who very much reminds me of you, although the circumstances that I got pregnant in were not consensual.
He was desperate I get an abortion, and eventually I was forced into it through fear I would be humiliated by him and his girlfriend (it later turned out his "girlfriend" did not exist and was just a lie he told me to put me off having the child). He claimed he was in love with his "girlfriend" and that I had no right to do anything other than get rid of the baby, despite the fact he had done exactly as he wished to me in terms of taking advantage of me when I was in a vulnerable position.
Anyway, I digress slightly. I feel strongly on this topic and I believe wholeheartedly that you do not have the right to interfere in her pregnancy, especially if you have no intention whatsoever of being a partner to her, or more importantly, a father to your unborn child. I suggest you accept your responsibility in this. You cheated on your partner, you got a girl you don't even like pregnant, and you want her to get rid of the baby to make your life with your existing girlfriend more convenient.
I strongly suggest you cut all contact with the girl you got pregnant, and allow her to make her own decision. Presumably she knows you have no intention of being there for her or the child, if not, tell her so. Otherwise, leave her to do with her body as she wishes. Abortions are very, very traumatic and their effects are long lasting and detrimental, I know.