Well, I didn't want a summon because those requires contracts and I found it quite unlikely for her to have written a contract already.
She doesn't have anything she can manipulate (like sand) to make the eye and... well, she needs something to make the eye of. Without the connection between her and the media used (Like Gaara had with his sand and Yondaime Kazekage with his gold dust) it just seems like it wouldn't work. The user of the third eye has to connect the third eye to their optic nerve, which they can do by the chakra, is suppose, but they have to be able to manipulate and control the eye as well. Otherwise, it is pretty useless...

Am I making sense?