Do your characters develop relationships? Think about all kinds of relationships as well as the obvious romantic/sexual ones. Is there part of their personality that makes forming relationships difficult? Do they find a particular type of character difficult and if so have you shown why?
How do your characters’ relationships change? Relationships don’t stay static. Relationships should be a major part of your plot, should complicate things and give your characters both hope and despair. Think about how your character demonstates anger, frustration etc.
Make sure when you use things from your own experience that everything you use you are happy to see in print (hopefully achieved!) and that nothing can come back to haunt you. Generally speaking it is best to, for example, use feelings and then get your characters to expand them and take them in a direction appropriate for them and the story rather than get your character to reflect everything that actually happened to you. Real life experiences should be treated like chilli powder - use very sparingly. It is your characters that matter. Characters should reflect, not copy exactly. The irony is that so often real life things tend to sound not real in fiction. There’s a reason for the saying truth is stranger than fiction… what you seek in your fiction is the sense of truth. You want folk to think yes, that could be. And don’t lay it on thick with a trowel. People will see through that.
Are your characters true to themselves? Fairies can be seen as twee - Eileen is anything but. Original fairy tales are often gory. You want your readers to hate your characters, love them, worry for them, wonder what happens to them after the story finishes but they must never be boring.
Do your characters adapt? They ought to. Any tale, regardless of length, is about changes - after all nobody in life stays static so your characters shouldn’t. Your characters should develop as we do in life. It’s in that sense any fiction should mirror life.