I need advice

How do I break up with a girl that I’ve been seeing and in a relationship with for 9 months

Over the course of the relationship I always knew in the long run it won’t last because of different religions and values.

I started to compromise my religion and be a part of hers and I am not happy anymore

Like I says she’s a really good girl and respects me and is there for me in every way!

How do I let her go? Its hard