Is it normal for an 8 month old baby girl to have pubic hair?

Pubic hair on girls at that age can have several causes. It can be a sign of early puberty, or of something called premature adrenarche (a benign condition that doesn't need any treatment). Generally, when pubic hair is present at that age, it is worth doing some blood tests to sort out the cause, especially if there is any other sign of hormone surges. Other signs could include a growth spurt, clitoral enlargement, acne, advanced bone age (shown on an x-ray), underarm hair, and body odor. Jumping lines on the height growth chart would be especially of interest if this contrasts with her twin.

Exposure to extra adrenal/steroid hormones can cause this, but it would not have been the ones she received before birth, so you can relax about those. They would have helped mature the lungs, but otherwise their effects are long gone.

If the pediatrician doesn't seem confident about what is going on, a visit to an endocrinologist could settle the question. But your pediatrician may well be entirely correct that it is not something to worry about, and just bears keeping an eye on if the rest of the exam was totally normal.

or, it could possibly be Progeria, which is VERY unlikely, considering the condition is so rare..