Of course it's normal.. Isn't the end goal of a relationship for most people just that? I'm gonna need a little more context to really understand why she was asking, but the discussion about kids and marriage will always happen between two people because you need to see if your future plans are aligned.
Well... how long have you been dating for and how exactly is she talking about these subjects? If I've been dating a guy for a while, I'd want to know what his views are on marriage/kids and all that eventually. Just to see if we have the same views or not, since that might determine what our future will look like (or not look like). If you've literally gone on only one date and she's already talking about what your wedding will be like and what names your kids will have, she's probably a bit crazy. And not in a very romantic way.