In a very real sense you cannot convert her.
There is nothing to convert her to.
Christianity is a way of looking at the world through a set of special filters that tell you everything is nice and rosy and all you have to do are a specific set of things and you get to live forever. There is a phrase: "I used to pray for a bike, but then I realized it didn't work that way so I stole one and prayed for forgiveness." That covers it in a nutshell.
Religion lets you justify anything. Anything at all. 200 people fall out of an airplane and into a vat of acid? The lords will.
You find 20 bucks in your pocket after the laundry? The lords will.
You can't convert her, all you can do is to read the bible with her, and ask her to explain what certain areas mean. Remember, the bible can mean anything, that tells you that it's meaningless on it's own. Use it as a tool to help you. Look up some contradictory verses, look up the parts about slavery and selling your daughter, or the multiple mutually exclusive ways that you can and can't be saved. Have tons of legitimate questions about the bible. Eventually she'll realize that she can't explain it, and say so, or she'll stop talking to you about it.
As long as you go about your life and live in a way that is consistent and for lack of a better word 'good' then you are fine. Be your own person, even though it may take a while to figure out who that is. Maybe someday you'll help your mother take those lenses off for a while.