Nina's reaction to being pregnant

Maybe it's just me, but I always thought Nina's reaction upon finding out she's pregnant, was a little unrealistic. Considering the circumstances, I didn't think she even really seemed surprised, her face just kind of lit up, like this was the best surprise ever. Now, I'd never think it a BAD thing for anyone to be happy about a new baby, but I'd think it to be more logical that her reaction be more similar to her husband's. I guess George was freaked out enough for both of them, but if I were in my late 40's with one child married, the other almost a teenager, and a grandchild on the way, I don't think I'd exactly be happy about being pregnant again, at least not happy right away. I'd be dumbfounded at first, probably in denial and insist the doctor must be mistaken, then, well, a little depressed, I mean, let's face it, most women wouldn't consider that a welcome surpise at that particular stage in life, at least immediately. I'd expect to become happier about it as the experience went on, but only after having some time to get used to the idea. I just found it a little odd Nina would be so pleased about it right away.