Unfortunately, "Terra" isn't her name, and now FFXIII has a character who's actual name is Terra...Another Woosley ace in the hole...! >_>
To me, Terra is just as generic as Tina (I've never even known a Tina)...it's just a stupid spelling of Tarah or Tara with a earthly connotation (that doesn't really fit Tina at all...)...Even if I thought Tina was plain, I'd still say it was a good choice because you don't need extra confirmation that Tina is special. She doesn't need a different name & she doesn't need green hair either.