As for Yu-Na, when she began in 2006 her spins (like her skating) were a little bit awkward and clunky, but still good with lots of potential. By 2008, she'd worked on cleaning up her positions and had increased her speed as well. Her back position in her layback is superb as is her speed; her centering is good; her arm and leg positions are average. Her Biellmann position was decent, but last year she bumped it up to good. Her layover camel position is superb; her sit spins are very good. Her combination spin has good speed but the positions are just a tab bit better than average. No, Yu-Na will probably never be as great a spinner as Alissa or Mirai, but she worked with what she had and improved upon it and, as a result, she's a good spinner.
I say all that to say, with some work, Liza's spins can get better too.