I know you may not think GS is going to be that much of a good experience besides boosting your WCS, but if I had to choose again between seminar and Girls State, I would choose Girls State. Right when I walked into the interview, they told me directly that Girls State is looked at more favorably and of course adds points to your score. Now, if you think about it, if you don't receive an LOA and nomination or a principal nomination and qualification, or a presidential nomination etc, Girls State is going to boost that WCS, which helps your standing on the NWL. You want to be the best of the best on that list. You want to be their pick. The WCS algorithm is going to make or break you. A few extra points could be the deciding factor for the future.
Not to mention that Girls State was the best experience of my life, I made unforgettable friendships and lasting memories, and met so many wonderful girls like me interested in serving this country. Some had attended a seminar most did not.
But on the flip side if you've been accepted to the seminar, then you probably are very well qualified. Therefore, going to GS is not really needed for you. A lot of applicants don't attend Girls State, but get in. So it's up to you! (although I'm completely bias to GS but it's really up to you)
If you want to find out if the academy is right for you, go to the seminar. If you want to fall more in love with going to an academy and serving your country while meeting and friending amazing girls like you and being immersed in a life changing, empowering experience, choose GS.