I'm confused, your OP makes it sound like you were the first to use the r word. Perhaps I'm mistaken.
If you did use it first, I'm not sure that you can complain about your friend's use of the word.
I'd also say that, understandably, this is a sensitive issue for you. Word choice aside (which I agree, was poor), often there's nothing 'right' a person can say. A lot depends on tone, expression, and intent.
If somebody tells me their mother just died, I could look them dead in the eye, take their hand, and say "I'm sorry", and it could be thoughtful and supportive. Or I could just toss out "I'm sorry", in a bland tone that's actually really hurtful.
It's very possible that your friend doesn't realise what a sensitive topic this is for you, and therefore wasn't paying as much attention to her tone and phrasing as she should have done. I actually don't see what she said as being all that bad, provided it was said appropriately.
In fact, in your shoes I'd find it more comforting than "the doctor is probably wrong", which I'd regard as a platitude, and I don't do well with those. I regard at somebody not wanting to hear about the problem, and just hoping it'll go away so that they don't have to support me. Maybe your friend feels the same.