Is it permissible to marry someone with whom you have had premarital sex?

I have had sex with an innocent girl of my age we both are muslims. I did not have the knowledge of haram and halal while performing the act but now I feel disgusted. She wants me to marry her but my parents are strictly against love marriges. Question: I want to know if this relationship would be halal if i convince my parents to get us married? I am afraid if this relationship would become haram as we have already indulged in the sinful act. I am very scared and I do not want to spoil her future. Please guide me in this as I do not want to let her go.