Baby girls

Yes there is actually a way to pick whether you get a boy or a girl. If you want a girl have your sim eat three watermelons when she is pregnant and showing. If you want a boy (I know you said you had too many but just for your future informations) you have your sim eat three apples. This works everytime and Ive used it many many times. :)

I just had a twins girl, and I like my elder daughter more, because the little girl always can't have a good relationship with her mother. and it seems the elder sister looks like her mother more. So I like my elder daughter.

This is very funny to hear that. I played Sims 3 before but my children were boys and girls and it's perfect. I don't know why you only have boys:) Just keep having more children and I am sure at the end you will have a girl:) I love China

What you can do perhaps is trying saving the game before your female sim goes into labor and gets the baby notice. If the end result is a boy (or whatever gender you don't want) than just return to the neighborhod and don't save the game. Re-enter and retry until you get your way. I've done that with Sims 2 at least and it worked. Another thing you can do perhaps is, if you have enough lifetime points, you can purchase the fertility treatment for your female sim. This perk will increase the chance your female sim has twins or triplets. The more babies that get spawned, maybe you'll get a girl? Finally, I've read through numerous sites in the past. The gender can be altered by what your female sim eats. If she has a craving for say something with watermelon, that is said to cause girls to be born. On the other hand, apples are said to bring boys. You can buy either fruit at the supermarket in your neighborhood, find seeds around town, or buy them and plant some seeds. Best of luck!