Characters based on real people: aren't they all? To protect the guilty, we change age, names, gender, ethnicity, but every one I've written has been based on someone I know, once knew or, often, wish I didn't.
Do writers ever worry that the person we've described as unfit for social contact will recognize himself? Here's a story that will ease your mind.
When I was a very new fiction writer, I gave my protagonist a friend who was based on an annoying woman I'd been forced to hang out with in real life. But I neglected to change her profile except to give her a different name. In the book, her name is Leanne. Here I'll call her Peri, short for persnickety. Peri, (the woman and the character) was prissy, nosy, and intrusive; she'd ruin a joke by correcting the smallest detail of your story and remove a nanopiece of lint on your sweater with a damning tsk-tsk.
When the book came out I did a signing at my home town library. My sister-in-law, who'd read the book, was traveling with me and accompanied me to the event. It had been a terribly humid August with a heat wave that was 17 days running, but on this night we were excited because there was the slightest chance of rain. The small talk before the event revolved around prayers for a life-saving shower. Except for Peri, who showed up carrying a folding umbrella that matched her shorts.
After a few minutes of observing Peri, my S-I-L leaned in to me. "That's your Leanne, isn't it?"
Suddenly I was worried. OMG, if my S-I-L, who'd never met Peri before could ID her from my book, I was in trouble. When Peri came up to me later, I was a wreck with worry. Here's the conversation:
Peri: You know that character Leanne in your book?
Me (gasping internally): Yes?
Peri (sotto voce): She's based on Verna, isn't she?
Me (gasping externally): Yes!
A few friends/characters on a special day
People read what they want to read into the characters in a book. Another example:
In my Periodic Table mysteries, I give my protagonist a BFF named Rose. Here are a few responses:
From Friend A: I know Rose is really me, because she has 3 kids, like me.
From Friend B: I know Rose is really me, because she's petite, like me.
From Friend C: I know Rose is really me, because she loves to shop, like me.
From Friend D: I know Rose is really me, because she has red highlights, like me.
And so on, to Friend Z: I know Rose is really me, because she drinks wine.
And, in some way, they're all correct, of course.