If you care about her feelings : make things clear about yourself and your expectations. Tell her you like enjoying your time and are not a one-girl man, at least whe will have the information. Of course, chances are it will not work

She will believe she is the one that can change you (extra chances it will happen as she's religious), so it will probably be somewhat messy to handle.
Honestly, do you believe that she could have casual sex with you without being hurt afterwards ? I dont. So either fuck her and let her learn from her experience, or forget about sex with her.