I had never heard of
Glynis before. I agree with you about the sparkly and sweet sound, but I think I would spell it
Glenys. I like
Glenna, but
Glenda reminds me too much of the Wizard of
Oz, even if that was Glinda.
I actually like the name
Glen (or Glenne) for a girl. A little weird, maybe, but I like it.