If you use her all over I would say go for it. If just a war tank, I say no. Obviously there are better purples to limit break, but if you are staying free to play, it could be months/years before landing that “premium’ hero. Roll with who you have.
As said, if you use her elsewhere then yes. Otherwise I’d lean towards Clarissa or Sartana (especially if you get her costume). All depending who you use more frequently. As f2p you work with what you get rather than wistfully waiting for something better.