I doubt it will be an act your age snipe more likely the reasoning is that a 10 year old isn't going to sell it on ebay. I doubt she'll be signing during the convention, just there for the promotion.
If she ever does a signing gig in the UK it will be one of the £60 to get in jobs as it will cost a shed load to get her in, beleve me I know how much it costs to get some of the Buffy cast and boy some of them can charge