How sweet of you I'm not good at coming up with ideas but I'll just list the stuff Nicole likes so if you have to have a last resort you can look at this hehe.
But Nicole's birthday is in October, isn't it? You're a bit more than 2 months early but you can always just give Nicole a present regardless of whether it's her birthday or not--fans do that all the time. Just like an appreciative present?
Nicole loves plushies (..right?) and piggies so if you end up running short on time you can always find something really cute w/ a pig cartoon on it. She's probably gotten tons of those, but I'm sure she'd appreciate anything she receives.
She also loves to cook and her favorite color is green (though it used to be orange). If you're thinking about clothes, her style is very tomboyish with a tad bit of hip hop influence. Maybe a hat? I'm sure Nicole will love whatever you get her!
Let us know what you ended up giving her!