Theory on Rubí’s ending
We all know how Rubí ends. If you don’t know, then stop reading.
Even though Rubí gets what’s coming to her, she grooms Fernanda into being just like her. It’s all part of her plan to get revenge against Alejandro and Maribel. In the final scene she succeeds. Alejandro enters his office and finds Fernanda waiting for him. He confuses her for Rubí and she manages to seduce him. The End.
Now there is a theory I have seen floating around. That theory is, that the ending was just a dream or revenge fantasy Rubí was having. She never met up with Fernanda in secret, to groom her into being like her, so she can use her for her revenge as an adult. Thus, Fernanda never seduces Alejandro. It was all in Rubí’s head.
To be honest this theory makes more sense. I think Cristina and Marco would have known if Fernanda was meeting up with Rubí. They would do everything in their power to keep her away from Rubí. Let’s not also forget that if she was going to the ghetto neighborhood where Cristina and Rubí grew up, the very same one Rubí tried to escape but ends up back in, Doña Lola, Onésimo, and Mariquita would all know. They would be quick to let Cristina and Marco know.
Therefore, I choose to believe this theory that it was all in Rubí’s head.