No, Jamie Lynn Spears is not in the Adam Sandler movie called Blended, perhaps you are confusing her with Adam Sandler's co-star, Drew Barrymore?
I checked out Jamie Lynn Spear's IMDB page, and there was definitely no mention of the movie Blended.
In fact, the only movie I recognized in her list of previous roles was her sister's feature length film: Crossroads.
It must be tough for Jamie Lynn to constantly have to live in the shadow of her more famous sister, Britney - but at least she has an IMDB page with some decent credits to her name, unlike some aspiring actresses.
