Yes, she was stupid, she was wrong - though on the scale of some other issues this is a fairly minor infraction. What worries me is as a society we seem to hold journalists, actors, musicians and anyone else in the public eye to a higher standard than we seem to hold politicians now.
I'ld bet that any people without media status or lots of money would love the ability to wiggle the rules for a 10 person party for an important birthday/wedding/funeral too. I'ld also imagine a lot of those people would be told "no way" if they did ask any business to weasel lockdown rules.
I can at least say I know that's the case as my parents had a staycation booked months ago cancelled as they were going to share villa with one other household in our family, and the company basically said "yeah we're sorry but we're also not going to risk anything, here's your refund" - now magnify that many times over with people who were maybe hoping to do a wedding/funeral or any other milestone event and likely had their plans cancelled while someone making very nice money at Sky gets to be above the rules and have their fancy do.
Kay didn't just flout the current advisories once for a party. If you believe what the owner of the second restaurant apparently told Guido (and it's not exactly something a business owner wants to admit to right now) - then Kay was there for quite a long time to water the roses and had more than a "few" people enter and leave the place. If any one of those people had Covid, that's a bunch of households who now potentially have it. The fact she did it knowing she was (apparently) going on holiday just shortly after doesn't really make it better. What if she gets to Africa and it turns out someone she invited *did* have Covid and she caught it?
Also consider this - what happens the next time another politician or public figure breaks lockdown rules and Kay's the main presenter on during that story? If you use her to press the issue (which is one of Kay's strengths as a Journalist) - well now the subject can rightfully counter that she didn't follow the rules as well, and she can't ask if someone will resign without potentially someone pointing out she's still at Sky. Heck even outside Covid, it's a potential issue for interviews over corruption or rule breaking for the short term.
That's not just the politicians you dislike who can take advantage of that. Tories, SNP, Labour, Greens or even Lib Dems will all be poised to deflect from their own rule breaking with a reminder that they did it too.