Couple things to think about
When someone finds something that is just absolutely amazing and life changing, for them, they are often compelled to share it with others. It is basically - "OMG, you have GOT to try this, it is delicious! No, seriously, just take one bite, it is AMAZING!" I had been guilty of this, myself, pushing martial arts on friends. I realized how rude it was and apologize.
If you are in the U.S. we ALL enjoy the protection of the 1st Amendment which prevents the gvt from establishing an "official" religion and also allows you (or her) to say (virtually) whatever you want to people. A crackhead could approach you and try to explain the wonderful benefits of drug use same as a Christian or Hari Krishna. They're free to pitch whatever ideology they want and you are free to respond however you want. I actually like it that way.
As for response, mine would be polite but firm and suggest that the polite aspect is subject to change. Something like:
"I am very happy for you! You've obviously found a path that works for you. It is NOT my path. I am not remotely interested in your religion and, while I am trying very hard to be as polite as possible, I am getting very tired of you trying to force your beliefs on me. I respect your beliefs, now you need to show me some respect by accepting I do not share them."
Or pepper spray her and yell "take that, ya jezoid!" I'm kidding don't really do that
