Update: My showcase entry has a character that looks like a friend, and I didn't get their okay. Is this a problem? | Digital Art Showcase - Vivisector
My friend got really quiet when she saw I'd used her tattoo design in a story without telling her. It's not just about looks, it feels like you took a piece of their identity for your project. That trust hit is way harder to fix than any creative disagreement. Would your friend feel used if they saw it?
Did you base the character on specific features or just a general vibe? In my experience, yeah, that can become a real problem. I used a friend's hairstyle and outfit for a comic character once without asking, and it took a lot of smoothing over. Your mileage may vary, but take this with a grain of salt, it's better to check with them.
Yeah the outfit thing reminds me of when I borrowed my cousin's favorite leather jacket for a concert and got a huge coffee stain on the sleeve. It was a whole thing, way bigger than just the cost to clean it, because it had this history I didn't know about. Sometimes you don't realize what a thing means to someone until you've already messed with it.