If you haven’t read The Selection series and don’t want to be spoiled stop reading here. Seriously. Don’t read any further. Got it? Good.
Although Celeste started as the girl to hate in the series she evolved into a girl that I respected and admired by the end of the series and I think almost everyone fan of the series can agree it was sad to see her go.
Besides that, however, when she did come around she became the champion of the Selection girls. Once she stopped seeing them as enemies and instead as friends she took that fierceness and used it for good, becoming one of my favorite characters. I especially loved her support for America and thought it was cute when she threatened Maxon, warning him not to break America’s heart. I wish more than anything that she hadn’t been murdered and we could’ve seen her grow up and be a staple in Princess Eadlyn’s (America and Maxon’s daughter) life. Unfortunately, that’s not the case but we can always reread The One, and imagine how Celeste would’ve brightened up America’s Women’s Room.
As we spoke, I could see [Celeste] being accepted by the others as fully as she was now by me. She even looked different with the weight of her secrets cast off from her. Celeste had been raised to be a specific kind of pretty. That beauty depended on covering things up, shifting the light, and seeking to be perfect at all times. But there is a different kind of beauty that comes with humility and honesty, and she was glowing with it now. – The One
Zakiya N. Jamal 
I am with you, I so much loved Celeste and was sad that in the last time, when she was in the books, it was so poorly described, as if she wasn’t important. But she was. I recently was discussing in my blog, if Celeste would be actually a better queen than anyone else in the Selection.
I don’t think she would’ve made a better Queen than America. Celeste didn’t have the experience with the lower castes that America did. Plus Celeste didn’t love Maxon and truthfully you don’t have to love your husband to be a good queen but I think it definitely helps.