Can I be sued for selling a picture of someone without their permission?

About six months ago I was hanging out with a friend when a macro lens I ordered arrived. She suggested I tried it out and let me photograph her eye. The image can out really neat, so I edited it and made some prints of it which I then advertised to sell on my online shop. A couple days after I took the photo she asked about it, I sent her the picture and she thought it was really cool. I also mentioned my plan to sell prints of it and she didn't have a problem with it then.

Flash forward to now, me and this person are no longer friends. No fight ensued, we distanced and lost touch. Today I get an email from her saying if I don't take down the print and give a percentage of the money made from it to her, she'll sue me. Can she do this? The photo was taken in my home, with her consent, and if she had no problem with it six months ago why does she suddenly have a problem with it now?

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