Very good answer.
OP, since you know she’s a wiccan, I assume she knows you are a practicing Catholic. A casual date is not out of the question. You might ask her about Wicca and how she practices it and also ask her to tell you what she thinks being a practicing Catholic means.
Depending on her frame of reference, she may not realize that being a practicing Catholic means accepting what the Church teaches and leading a family in the Church. Not that you are going to talk marriage right away (although some people that do the online dating route get to that question sooner rather than later) but she should understand that your faith is not just a “me and Jesus” thing but that it affects all areas of your life.
It’s too earl to talk about “breaking it off” if you haven’t even dated yet.
P.S. If you DO date and DO get serious, seek counseling earlier rather than later. The Church is pretty serious about mixed marriages but many people go into pre-cana in a “love haze” and don’t think any of the challenges will happen to them.