In this situation, is the outcome of the Istikhara prayer an indication that the matter is evil, and can God avert evil if I proceed with it, or will evil occur as God has warned? And is the dream that included marriage, childbirth, and the envious person a true vision or a mere dream, and is its interpretation clear or does it have another meaning, and what is the meaning of the envious person's presence in it?

Familiarity between young men and women under the pretext of marriage is a door to temptation. Informing suitors about past sins is a path contrary to Sharia (definition). The correct approach is to conceal one's past, and what matters is a person's present state, not their past. You must end the relationship with the girl. If you wish to marry her and she has repented, there is no harm, for repentance erases what came before it. Interpreting dreams is not within our purview. The preponderant opinion is that one who performs Istikhara (definition) should proceed with the matter afterward, and whatever happens, whether ease or difficulty, is what is good.