... what can I say to her to make her see religion is good?
Why would you lie to her...?
I have tried talking to her once and it went alright. I really like her yet this is important to me. As it should be.
Then you may be forced to make a decision between her and this.
Please give me advice on what I can say or do to show her about Christianity.
That's such a broad topic. She could start by reading some church history, theology, going to church / mass, etc. If she's not into it, it won't have much impact however.
Or maybe advice on how I can slowly bring her closer to God.
She could already be close to God. Who can say?
I hear prayer works well, if you're a praying man. I'd go with that.