All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
We ask Allah to help you stay steadfast on your religion.
Know, dear brother, that it is unlawful for you to talk to that woman because the Sharee'ah forbids talking to Non-Mahram women except for a dire necessity that cannot be achieved otherwise. The prohibition is more emphatic in your case as this woman is still young and you have a desire to marry her as you mentioned. In fact, talking to this woman might lead you to looking at her, touching her, etc. and this is firmly prohibited.
Al-Khaadimi (a Muslim scholar) said: “Talking to non-Mahram young women is unlawful as it can lead to temptation.”
Kash-shaaf al-Qinaa' reads: “And if a man greets her; i.e. the young woman, she does not have to reply to him in order to avoid any kind of depravity.”
But, you can call this woman to Islam through your Muslim mother or sister. She can talk to her and tell her about the benefits of Islam and that Islam is the seal of all religions.
Allah knows best.