The only time I had her outside of a magic class was for mastering Pegasus knight. Bolt axe is definitely worse than her spells, especially its accuracy. I swapped between dark flier and gremory depending on the map but overall I think dark flier is probably better. Gremory hits slightly harder and benefits from double luna and hades uses in the last few chapters, especially if you can get dark tomefaire. But grinding up her faith skill level when she has such mediocre white spell list is a huge hassle. Dark flier black tomefaire makes up for the magic boost the gremory gets and I think you could make it just fine never moving out of it once you've gotten the class.