Sua was, in fact, correct. Yui Mat was standing in the same spot, yet elsewhere. Somehow hidden in a fold of the same space. Stupid lousy time-space distortions! This would be the same case for the warp drive as well, though it's not shown in this panel. It doesn't help that Yui is at a complete loss for words, unsure of what's even going on right now. Her current focus is on finding the other two. Which would be distracting her from fixing the warp drive currently.