Relationships and green cards?

Okay, so I met this woman who is from the Philippines through Yahoo Personals, we have been communicating through cell phone, internet chat, physical mail, email,text messaging, instant messaging since November. I am a filipino born in the United States. And we have every intention of meeting physically in person sometime later this year. I may be going over there through a missionary trip near her hometown of Manila. I was wondering, for those who have experience, how can I tell if this lady I am going to meet up with is only after my citizenship so she could get a green card? I have been very careful to listen and read every word this lady has said over the phone, text, and mail. Yes, I am wanting to get to know her and see what goes on from there. I am very excited but yet cautious. What are some points to know about a situation like this, her only after my citizenship so she could get a green card?