Hi, Shadows Mom,
I know how you feel – I’ve gone through a lot of products over the years that I didn’t use up because I learned more after buying or the bunny rejected it for some reason. (I think it’s one toy played with for every 5 purchased!)
Anyway, I would recommend discontinuing this type of pellet. The best pellet for a bunny throughout life is a plain one, preferably a ground timothy hay which is Oxbow Bunny Basics T. Some feel it’s OK to give a very young bunny a small amount of alfalfa pellets, but you don’t have to since they need to be cut back later. The nuts and seeds may be harmful, but also the mix you described is very fattening. Your bunny will develop a sweet tooth since it tastes like treats. Better to get her used to switching now and treat her with raisins occasionally so that you can regulate her intake.
Be sure to give her unlimited hay and water all day. That keeps her digestive tract healthy and she’ll only eat when she’s hungry, but it’s the best staple for her diet. Daily pellets and greens, simple ones, are the next item in the dish.
Have you posted pix yet? I’d love to see her! 
EDit: Hi, Beka! That’s a great idea. I have definitely brought opened bags of stuff back to a store to exchange. At least at Petsmart I had no trouble at all – they made it clear it happens all the time.