She still exists

"She's out right now," Ruby said with an annoyed tone. "She won't be back until...I don't know when she'll be back, but this isn't your dorm!"

"I know, I know," Jaune said. "I was just coming to get my mannequin."

Ruby looke to where the Yang mannequin now stood.

"Right, thanks for letting us use it," she said. "It really helped us see if our new uniforms would fit."

Jaune snickered inwardly at Ruby unknowingly viewing her own sister as a mannequin, but thinking Yang was out somewhere.

Now that Jaune knew the collars worked, he could collar Ruby right now...