The best way to get her to stop "bugging" you about religion is to invite her to sit down with you and have a heart to heart conversation about what you believe and why you believe it.
Act like a mature, responsible adult. Be patient with her, respect her, ask her questions about what she believes and why she believes it. Without even knowing what it is that your Mom believes, (or for that matter, what it is that you believe)I feel confident that you have nothing to lose by having this conversation with her.
Who knows, perhaps it is you that has a grasp on the truth; (ie: that Jesus Christ is Lord) and you would be able to reach her with that truth, bring her to repentance for her sin, and keep her soul out of hell for all eternity.
I suspect that the reason that she keeps "bugging" you is because you are her child, and apparently she has an invested interest in where you spend eternity. It is the most important decision that you will ever make, and you never know when your last chance to make that decision will be.