To be fair, it's a bit inappropriate to tell your coworker she looks cute. Maybe compliment her outfit instead. That said, she could have told you directly then or in an email just to you. CCing the whole office was highly inappropriate as well and pretty mean-spirited. (Unless this isn't the first time you've said something like this to her and she's asked you not to.) The proper thing to do is apologize and tell her you won't do it again.

As a woman, I can say this: I definitely would not have sent out an email about it, especially not to the entire office, but this would have made me feel uncomfortable. Calling someone cute is an innocent enough thing to say. I'm not arguing that. But it's hard as a woman in the workplace, especially in fields like tech and engineering that are male-dominated, and honestly if you're a woman you have to be twice as good as any man in those fields in order to get half of the respect and acknowledgement that your peers get. You might get awards or public recognition from the company, but you know that deep down 99% of the men in that company will think that you got that award or recognition instead than them just because you're a woman, and that the company is trying to look "equal-opportunity." It's really difficult and frustrating, and it wears down on you. So if you're in a situation like that, even something as innocent as being called "cute" can remind you that people aren't necessarily looking at you and seeing all of the hard work, dedication and intelligence that led you to landing your job. They're just seeing what you look like, and it's really ******* depressing at times. Way more than likely, the comment was totally innocent and was just intended to be a compliment and to brighten this woman's day, and I'm sure OP is a great guy. Just keep that in mind.

unfortunately, some people think a minor compliment means they want to sleep with you. some people seem to think just looking in their general direction means you're hitting on them. just make it clear with HR or your boss that it was just an innocent remark.

Actually, she is right (and I am a man from a third world country). You think you complemented her, but all those words brought her down to is some 'thing' to be seem 'cute' or not, a gender based discrimination, as opposed to a 'person' with actual competence, importance, and relevance at work, and in general. If she is did look pleasing to you, a more neutral way to express that in future is to complement her by something like, "you look lovely/lovelier than usual today", or "those clothes look great on you" - if you have a trusted rapport with her already, not if she is a stranger. Try to not make it sexist or demeaning, and this can be done by the use of the right vocabulary. The shade of the meaning can be different.

it could have been worse...she could have claimed rape and your life would have been over. regardless of what really happened

damn......

How do you not realise this is sexual harrasment in this day and age?!?!!?

I once got told I looked cute by a guy on the first day I came to work wearing the same uniform everyone else was wearing. I sarcastically said thanks (though I don't think he picked up the sarcasm in my tone), but I wish I'd said, "Yes, this uniform makes us all look rather adorable, doesn't it?" instead.

I would get HR involved, just to be on the safe side. Telling her she "looks cute" is a tiny tiny step over boundaries ("nice jacket" would have been more appropriate), but her rather vague email to the entire office def also crossed a boundary - it implies that you may have intentionally harassed her with something far more forward, suggestive, or even sexually explicit. Acknowledge that your choice of words may have not been 100 % ok, but that her behavior is also not ok. Create an official record before office gossip gets worse.

It's all about how you say it. Tell her she looks cute versus telling her you like her outfit and thinks she looks nice is different. I'm with her sorry.