Mollie is not 'creative' in the same way as L-a because, in regular English spelling 'ie' and iy' at the end of a word signify the same sound. They are genuine alternatives.
Spelling has evolved over centuries and keeps on changing, but it does follow certain patterns or rules. It can't be entirely random, otherwise written communications would be extremely difficult - and word-based computer programs would be impossible to use.
In different languages, each letter has it's own sound. Which is why 'Aime' as a spelling for 'Amy' in English (or French) does not really work. Normally, in English, a final 'e' is silent or is a 'uh' sound or softens the consonant before it. So following normal English spelling, we read 'Aime' as 'Aim' or Aim-uh, not as Amy. That does make me tooth-itchy, I'm afraid.
The - (dash symbol) in L-a is a punctuation mark, not a letter. It has meanings (either to mark the sudden end of a phrase or to indicate a space between words) but it does not in normal spelling signal a sound. We don't write, for example, 'I -ed to the shop to buy some more bread....'
If people like the name Ladasha, then why not spell it Ladasha or even Ladacia...