Yikes. It would have been one thing if you'd pointed out to her your reasons for denying her way-outta-line request, and she'd been appropriately shamed or at least chagrined. It would've been bad enough that she put you in that position. But her reaction was a blaring siren — FAULTY CHARACTER ALERT — and there's no saving a friendship after that. Like your other commenter wisely notes, it's her loss.