I agree. I never stick to just saying "happy birthday" because that's boring. It depends on who it is, but I've said such things as "Oh hey, I notice that it's your birthday. Good for you!"
But of course she'd have to have a sense of humor.
Maybe come up with some convoluted way to say happy birthday.
I also sometimes include a variation of "you're one year closer to death, so enjoy being alive" or some hippie s*** like that.
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~Halo Now darkness takes you... forever.