Be patient. Be an example.
When i was 14 i became a Christian of my own choice. I grew up in a 'church' family. My dad was always a Christian, just didn't always act on it. Similar to your mom. I spent the next year going to youth group, unfortunately it didn't do a lot to help me grow. But after that year i got into a new group of people that went to crack town to witness. We also started having bible studies once a week. It really helped my faith grow, my boldness, and i just naturally expressed my faith. And since so much of my life revolved around church, witnessing, Christian music, etc.. my conversation often went that direction with my dad as well, just naturally. Telling him about my day, or what happened when we went witnessing, going to the Christian bookstore, etc.
Overtime my dad began being effected by my walk. I wasn't really thinking to effect him, i was just being myself, and talking about my life like normal. But he saw my enthusiasm, and commitment and he actually started coming to me asking questions about my walk.
My dad is well versed in the bible, so it came as a shock to me when he started looking to me for answers about how to renew his walk. He began going to church again, started reading his bible, praying.
So my suggestion is, just grow in your walk, especially if you're a new Christian. New Christians often mean well, because of their lack of knowledge they can sometimes backfire when they try too hard to speak up and be a witness. So just grow in your walk, let your new life show, don't push it in her face to get her to notice, but also, don't hide it. Just let it come out of you the same as telling how your day at school went. Or how a movie was.
Eventually as you are more learned you can start trying to speak specifically to her about things. Just keep praying for her. Also, remember, its not your job to get your parents saved. I mean, if you are able to be the one to lead them to Christ, that's awesome, but it's not on your shoulders alone. It could be someone else. You just do your best to live right in front of her, and be open to chatting with her about it all. But don't let yourself feel that you have to be the one.
Hope this helped some. (=