What's the Name of That Book??? discussion

Read in around 2019-2021, aimed at middle school age most likely. A girl and her sister, (maybe named sofia) find a magical world in their aunt's attic, climbing through a ladder and ending up in a well. The aunt disappeared, they later find her in the world. The title had something about unicorns, as it mainly revolves around the last unicorn in the world. I think the sisters go to a school type place there, and meet characters called cenna and nett, and they have like powers with the elements. I'm also pretty sure the older sister, Sofia?, turns into a unicorn, and gets hunted. I also think it was a trilogy, and the cover had like a unicorn silhouette.

This sounds like The Unicorn Quest trilogy by Kamilla Benko. The books are The Unicorn Quest, Secret in the Stone, and Fire in the Star. The main characters are sisters Claire and Sophie, and there are characters named Sena and Nett.

SBC wrote: "This sounds like The Unicorn Quest trilogy by Kamilla Benko. The books are The Unicorn Quest, Secret in the Stone, and Fire in the Star. The main cha..."
YESS!! Thanks so much!