I would argue there's a difference between "I'm struggling getting the tone I'm striving for so I got some help by using AI to adequately convey what I feel," and "I asked AI to write a letter to intentionally convey feelings that don't exist or misrepresent them." I would further argue that if you're giving a Christmas card to someone, the former is 100% okay and the latter is manipulative in the way they say people pleasing is manipulative. It sounds like @retro_chic is doing more of the former.
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I'd say if it's bothering you, bring it up, but I would also say if it felt authentic and you never claimed you made up and worded the whole thing yourself, don't sweat.