They started around 2013, but she had presented the idea a year before that.
Daron "created" Star when she was 10-11, literally making herself as the main character and using Sailor Moon for design, then adding ideas from shows like magical knight rayeheart, card captor sakura and a large etc (there are many coincidences from different shows and even movies) nothing wrong with it at first glance, usually people inspires in different stuff to create "new" stuff.
The problem comes when you realize that Daron had the show in her hands for a while, around 15 years and few to nothing had advanced.
In "lore" department (everything was Star imagination so there was no real advance), she didn't have a show in mind(the ideas were that she was trying to help a kid to recover his tricy, some shit about some stairs and her imagination thinking she was escalating the stairs of doom to confront some evil that is implied to be bullying, but then her designs always depict adults as really hideous people) just some ideas for some comic pages, some references for background characters (Sol/Marco was Star's enemy in theory but they had no story what so ever) and that was it.
Disney and general media made a HUGE, HUGE emphasy on her being a woman and Star being "a different kind of princess" every single interview had to mention that both Daron and Star were not the usual glass of water, but I totally feel that other princesses made and still make a better job in representing strong girls better than Star (Elena de Avalor for example).