There's absolutely no reason why Cyborg couldn't make 135, other than she simply doesn't want to. To make the cut she would need to change a lot of her current processes, such as cutting out a lot of the supplements she's taking, eat a clean healthy diet, and trim down some of that muscle. She would lose a lot of her power in the process, which would make it a level playing field. She simply doesn't want to do it. The gif below shows what happens when Cyborg faces an elite level striker, she gets ripped a new one. Ronda would absolutely kill her.