Can I wear a maxi dress to a sister's graduation?

My sister's graduation is tomorrow (high school graduation) and I have either a white tube dress thats super flowy and summery BUT i wore that to last years grad and I hate repeating outfits for same occasions, but I just bought a really cute maxi dress:a href="http://www.forever21.com/product.asp?catalog_name=FOREVER21&category_name=dress_maxi&product_id=2000014615&Page=4&pgcount=25" rel="nofollow"http://www.forever21.com/product.asp?cat…/a some friends say the maxi dress is too much just for a graduation but I dont know!