First of all, you are not alone. You are joining over a billion people who embrace the teachings of the one true Church established by Christ himself. Secondly, it will likely take some time for your Mom to come to terms with things. At some point, I would invite her to a Mass. Most non-Catholic Christians have no idea what happens in Mass, how much of the Bible is read, how the prayers come out of Sacred Scripture, etc.
If she doesn’t come to terms with it in the short run, she will figure it out in the longer run. There are a ton of people all over the world in RCIA going through exactly what you are going through. Again I state that you are not alone. God the Father is with you, Christ is with you, and the Holy Spirit will soon dwell within you when you are sealed with His gift at confirmation. In addition, Parishes of the faithful all over the world will be praying for you throughout the process.
If I might make a small suggestion, consider trying to pray the Liturgy of the Hours from time to time. I find that praying with the words of God in the psalms and knowing that all over the world the universal Church is praying the same thing with me, helps me to focus, but also to see the true scope of the Church and that we are all one body in Christ. Secondly, if you have not already done so, try to get to know your RCIA team and your fellow inquirers outside of class. You are all in this together and having a social network that understands what you are going through and why you are doing it will likely be a great help. Our RCIA group got very close outside of the program by simply starting off with things like grabbing breakfast after Mass and going out for a drink after class. Those small things morphed into larger friendships built on a commonality that we shared of trying to come into the Church.
God Bless!