The only way I'd consider Ranka as a lolita would be if Ozma was her love interest.
I hardly think Ranka's 12. She is in highschool, after all. Besides, we already know that the Vajra incident involving the 117th research fleet happened 11 years prior to Frontier. If Ranka was only 12, she would have been an infant when the attack occurred and certainly wouldn't be old enough to have a repressed memory of the incident. Add the fact that we see a picture of Ranka as a child at around age 4 or so from before the attack on the research fleet. Unless the writers of Frontier are lying about when just about everything takes place, it's pretty impossible for Ranka to be a 12 year old that's labeled as a 16 year old.
Besides, why would the producers even care about what us Yanks think about something that will probably never be released here?