My thoughts are (as if I haven't already spouted enough
) that the more she sees you dithering, looking like you feel guilty and on the brink of changing your mind, the more she'll keep pecking away at you. If you could only appear strong and resolute to her, she might just have to face up to the situation.
The best thing you can do for her now is to put in place (as I've said on other threads) some ways that you can still keep in touch so she doesn't feel so distanced from you. Obviously the Internet would be the best way, especially if a webcam was involved, but I don't know if she's computer savvy. Of course, she may refuse any kind of help in that direction, but at least you'll have done your best.
And remember, many, many other people have left close family behind and probably more amicable ones at than your mum, which would have caused them a lot of pain, so it is doable.
Sorry, Lou, our posts crossed. See you've already made up your mind. 