Prepare for big wall of text on theory. (tl;dr part at end of post.)
I have my own theory on Summer Rose, but I feel it's more convoluted than it should be. However, when I notice these small details in Volume 2, I could only jump the gun on this and imagine the possibilities that this would bring if this was the case, and how it got there.
So my theory is simply as thus: In Volume 2, during the scene where the girls and Oobleck were on the train, they jump into the carts of the train. Yang stays behind to fight Neo, who generally stays very silent and smug through the whole series.
As Neo was about to finish off Yang, suddenly Raven, Yang's mother comes to rescue her.
Now there are a few things to notice in this specific scene. First off is that notice the jewelry around their necks. They look oddly, yet definitely similar, in design and as to how many there are. This kind of detail can be thrown out the window though as... well, women, jewelry, kind of a thing.
But the second piece to this is Neo's eyes. Neo's eyes specifically change from brown/pink to pure silver, and as everyone knows by this point, Summer Rose, Ruby's mom, were the same, in having silver eyes. This one you could make the slight argument that it's "vanilla" color, as Neo herself is based of Neapolitan ice cream, Vanilla, Chocolate and Strawberry mixed into one container, BUT I ask this... through the whole thing, Neo almost always used Brown and Pink eyes, no matter what the circumstance... So why is it that during this one specific moment, both of her eyes change to Silver? (Vanilla if you're still arguing.)
After that though, the other small details are how small Neo is compared to Yang, her hairstyle being similar to the one seen in the picture of Team STRQ, and to top it off, Neo being so scared, worried, afraid in that one single moment, when every single other time Neo has been seen, she has been smug, cocky, great at fighting and can woop on people... But running away from Raven specifically?
My conclusion is this: I don't know how, I don't know why, and I don't know what happened to Summer Rose, but with these things factoring in at once, I have a very suspicious theory that Neo is Summer Rose. (But in the grand scheme of things, it's a theory, and I'm sure can be debunked pretty hardcore, and proven, if someone wants to be that guy, but hey, I'll have my fun with my own thoughts if that's the case.)
Phew, long post is long. tl;dr, My theory is that Neo, the one smug character in the series, being scared of Raven, her eyes changing to silver for just that moment in V2C11: No Brakes, being so short, hairstyle and even the necklace jewelry matching Raven's, I'm starting to think Neo is in fact Summer Rose. (The end)