Religious christian mum forcing her beliefs on me. i dont know what to do?

What would she do if you completely ignored her when she started her religious rambling? Do not respond to anything, do not argue. Let her say what she's going to say but don't entertain the situation. Stare at her blankly then go back to your TV show (or whatever). Honestly...what can she do about that? Beat you? Well that would be domestic violence and against the law. Unfortuneatly you are in her house so she has the right to express her opinion, but that doesn't mean you have to listen. You can always tell her "this topic upsets me so I choose not to discuss it with you" ...and say nothing else about it.