>>13837I'm a serial minor character fixator and I do it for both male and female characters, however for the almond to activate over a female character she has to have a genuinely cool/cute design with little to no fanservice and not be a love interest to a guy. This is my criteria for fave female characters in general and you'd be surprised how many get struck out by these two categories alone. If it's a main character I'll also need them to get to do plot relevant stuff without being sidelined in favour of a guy (common with shonen heroines) but extremely minor characters don't need much other than to look cool and have the hint of a neat concept.
I'm also less likely to become fixated if there's no shipping options (F/F in the case of girls). That's the difference between 'character I just want to draw fan art of' and 'character I will write fic about'. I will say that it's easy to find obscure girls who are cute, but interesting quirks/personalities are less common, especially in gachashit, where blandness is default. It's almost easier when you have a total blank slate such as a cute generic NPC Pokemon Trainer class design, then the sandbox is yours.