Her hair is ridiculously awesome so I'll help you out ^^
Truth is, different people have different kinds of hair. So, what works for her might now work with you. I don't wanna get all cliche and say find your own style/ be unique/ be you because you like her style. So, I'd recommend bringing a picture of her to your hairdresser or a stylist and she'll get the bangs right. Watch the videos on how to do the poof. Looks like she doesn't need any products so cost shouldn't be an issue.
Here's a good answer to the same problem.
Her style is pretty rocker chic/trendy/scene/stufflikethat.
*bracelets (preferably thin) and plenty of them.
*one or two highlight streaks on hair?
= they look like her staples.
I don't think she wears that much. Either way, all girls do their make the same way. Eyeliner seems to be key.
Uh, didn't really pay attention to her shoes. I think she looks like hightops/converse kind of girl. So aim for those! She looks pretty casual/rocker.
Singing...Well I guess you could pay for lessons. Or get some of her songs on your iPod and lip sync? That's what I do and it works pretty good for me.
For make up you would have to wear eyeliner on the bottom and lower lash line and mascara.
For the hair,I think it's a scene girl hair cut.
Clothes: Wear skinny jeans. Get graphic tees that have cool stuff on them or say stuff on them. They have good ones at Delia's. go to delias.com
Make Up: Eyeliner. Maybelline Volum' Mascara. Etc...
Hair: Add volume to the hair on the back of your head. Get side bangs if you don't have them.
Singing: If your voice isnt very good, get a singing coach if you can afford one. They can help your voice with vocal excersises, but they dont work all the time.
Hope I helped:)
One, i must say that u r awesome because you like christina grimmie also, and two, i believe she has a hair tutorial on her youtube account... The rest you may make up yourself. And another thing, for singing like her, i would try to make your own style, which im sure she would recommend too