When we last saw Cipher in The Fate of the Furious, her machinations had been foiled by Dom and the gang, but she managed to elude capture.
Dom had been helping Cipher because she was holding his son hostage, but once young Brian was safe, Dom turned the tables on her, so it’s no wonder she wants revenge.
I suspect fans will have to wait until F9 is playing in theaters to learn the answer to the first question, but regarding the second, it looks like Cipher has a hand in getting Jakob Toretto out of jail so he can be involved in her latest scheme.