1) Every indication of scripture is that your good works have absolutely nothing to do with your salvation.  You'll find in Romans 11 and Ephesians 2 that Paul explicitly says that it is by grace and not by works that you may attain salvation.  That grace is the grace of Jesus' forgiveness that is taken on when you participate in his saving act (namely his death, burial, and resurrection) through baptism (see Acts 2, Romans 6, and Colossians 2).  Jesus makes several claims to exclusivity, that is that he is the only way to achieve this salvation (which makes sense since it is taken on the participation in his sacrificial death).  The most famous of these statements is in John 14 where he says "No one comes to the Father except through me."  You will see here that good works are not a part of any of that.  Living a good life is good, but never good enough to get you in to heaven, because as Romans 3 reminds us, "all have sinned and fallen short of the glory of God."

2)  Will she burn in hell is the wrong question.  Should she be uniting herself in the flesh (the Bible unequivocally calls marriage becoming one with) with someone who is not in Christ?  That's a better question.  It would seem to me that the indication of Scripture is that she should not.  This comes largely from 2 Corinthians 6 and 1 Corinthians 7.  In 1 Cor. 7, Paul lays out the hardships of marriage and why he believes it is better to be unmarried and in it he takes a particularly long time explaining the issue of believers married to unbelievers.  There is no prohibition here of marrying unbelievers, but that is because the couples in question consist of one member who was converted after marriage and the other who was not.  Certainly Paul would never have conceived of why a Christian would want to impose upon him or herself the trial of being married to a non-believer.  This is in part evidenced by the statement in 2 Cor 6 that believers should not be bind themselves to unbelievers.  In short, I think the idea of Christians marrying non-Christians is ill-advised all the way around.  Marriage, according to Paul and common sense, is already a complicated affair (let me tell you, I know).  No sensible person, much less a devout Christian, should think to deliberately complicate it by marrying someone with a fundamentally incompatible world view.

3) God can certainly work without you acknowledging Him and there are instances of that in Scripture.  However, God has never abstracted Himself to the point of being a guiding force or an inner light.  The way He interacted with the world was always bold and always overt.  He did not hide Himself from us.  Should you acknowledge that "inner light" and cultivate it with study and religious devotion, you may find that it was God after all.  You may also find that it was just your conscience or some personal standard of good.  However, you cannot presume that a God who spoke verbally to Moses on a mountain top and became incarnate in order to die would think it was acceptable for you to label your guiding light Him and pretend that you are following Him.