How to address an issue with my Mother about my Muslim GF?

Well this is uhh….tricky..and also pretty lengthy so I apologize for that but I REALLY need help with this one.

I come from a Christian family (although I don’t do the whole church thing) and my gf comes from a Muslim family, and she’s not exactly religious herself.
For me, that’s not really a problem (obviously). My gf has BPD, doesn’t “do” people. Not a people person. But when you get to know her, she’s really nice (not a word I like to use but it’ll do), funny, quirky (with BPD – so that works either well, or not well at all), she’s a really good person to know and to be with, despite her mental health issues, which means that I need to be able to handle things when she might have an “off” day.
My real problem is with my Mom.
My Mother seems to be hellbent on meeting her, which is understandable I guess – my gf and I have been going out with each other for almost a year now – but she’s lately been trying to find ways to force the situation. I’m in hell between trying to keep my gf from situations she isn’t likely to be comfortable with, and trying to keep my Mother from just ‘turning up’. Which she wouldn’t usually do, but I suspect she may well be working on it.
What aggravates me more so, is that thanks to bad media coverage, I suspect my Mother has tarnished EVERY Muslim as being a terrorist wannabe which REALLY f**ks me off. They’re not all like that, and aside from anything else, my gf is more likely to harm herself than she is likely to harm anyone else.
I’m not sure how to really go about putting my foot down with my Mother without having things escalate into choosing between my gf and my Mother.
Last weekend my Mother phoned and said she was coming up – I managed to stave that off, but she did seem very pissed off and was about to hang up when I said I would visit her instead (she lives a fair way off from me).
I’ve told my Mom that my GF will need time to get geared up for meeting someone she’s never met before, and her argument is that having been in a relationship for nearly a year, then maybe sooner would be better than later. Argh, she just winds me right up.
So aside from getting really mad with my Mom about trying to barge in uninvited or just turning up with a moment’s notice (which she knows I seriously don’t like), what can I say to try and get her to be more patient and to wait until the time really is right for them to meet up?

This probably sounds all so trivial and pathetic but it is a big issue. I don’t want my GF to get all weirded out or start having panic attacks etc etc.

Any words of wisdom on this one would be really good about now.