Is it wrong to be a little vain?

I took my daughter to her yearly check-up yesterday and I had a very vain thought, and was a little upset with myself after having it.

First of all, let me explain that some of the women on my husbands side of the family are just naturally very tall and slender, where as I always, since being a little baby, have been a little on the short side and have always had to battle with food to stay anywhere close to slim.

So, moving on with the story, the doctor mentioned yesterday that it looks like my daughter may turn out to be quite tall and has what looks to him just a naturally slim frame, because I was slightly concerned that she seems to be a bit underweight despite the fact that she would eat a stick of butter if I gave it to her (I never would, don't worry). Having been both slim and very overweight, when he said this my mind immediately went to a place where I thought "HALLELUJAH! She didn't get my genes!!!" And I was immediately a little ashamed for thinking it.

It's not that I lack confidence in myself or don't believe in teaching my daughter healthy eating habits and loving herself from the inside out, I just know how much my weight problems have affected my life. I also know from both sides of the spectrum, and I hate to say it, that people treat you differently when you're slim. I don't know whether that is a confidence thing or a twisted reality of society, but I have always felt that way. She is developing wonderfully in every other area, and I couldn't be happier about that as well. But I felt so bad about being happy that she seems to be developing more like the women on my husbands side of the family than the women on mine. Is it horrible to have such vain thoughts?