Friend helped herself to my birthday cake - is she ill or rude?

[Topofthecliffs]

I had a birthday party as a fundraiser for a charity on Saturday. I invited all my favourite people plus a friend who has been behaving oddly and has been rude and abrupt recently.
We had a live band and planned a cold buffet during the interval. Timings were band started at 7pm, supper at 8pm then more music and dancing.
At 7.45pm the strange friend approached DH and told him some people were very hungry and the food should be served now! He explained it would be soon.
I took the covers off the buffet at 7.50pm. She happily dived in and filled a big plateful. At 8.45pm the band played happy birthday, I blew out the candles, and took out a knife to cut the (huge and beautifully decorated) cake. I went to fetch some napkins to serve the slices on. As I turned to the cake I saw SF pick up the knife and hack a big triangular slice for herself from the front. She made off with it to her table. We were all astonished and have been trying to understand why she thought this was appropriate behaviour.
For info she is 70, a highly educated professional, but socially awkward. She has been becoming increasingly impatient and anxious in cafes and hotels at meal times wanting to get in as soon as the doors are open and wanting to be served first. She sometimes takes other people’s orders if they arrive before hers eg a cappuccino
AIBU - yes she is unwell and you should be compassionate - no she was rude and behaving like a greedy toddler.

I cant believe all of the people saying you are making a fuss about this. In my experience thr serving of the buffet is perfect timing. Would never expect it the minute you arrived!
The cake cutting is very very rude. If nothing else you could have a) wanted photos or b) what if that wasnt even the cake you were serving but instead you had popped away to get a tray of cut up cake and save that on for your family. It's very rude behaviour from your friend.

Yes, that’s part of the buffet, it’s not got candles on I suppose.

This

The hacking a lump out of the front of the pristine cake reminds me of the pic of Suella Braverman's wedding (just why???)

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People are giving you the obvious answer which you are ignoring. You state this strange behaviour is recent. She's 70. She needs to see a GP.

I’ve started to feel as though I’d really enjoy wading into a cake inappropriately at a formal occasion, reading this thread. Alarmingly, I’m going to a wedding this month. I hope I contain the impulse. It sounds kind of enjoyable. Isn’t there a cake smashing trend? Or has that been and gone.

You're coming across as a kind and thoughtful person @Topofthecliffs . How lovely to donate to charity rather than asking for gifts for yourself. Fwiw I love receiving presents (and don't like throwing parties.!)
Some posters have delighted in taking the wind out of your sails.
I hope your sports friend gets the necessary help she seems to need.

I think this could be an early dementia symptom. It sounds like she is quite disinhibited and this sounds a bit like 'Utilization' behaviour (which involves using an object for its purpose (i.e. knife to cut cake) regardless of whether it is appropriate or socially acceptable).

Well it’s clearly very rude but also very odd behaviour. It sounds like the start of something to me, dementia etc. Nobody in their right mind would do that, because everyone will be staring and gossiping about it. I hope you managed to enjoy your cake and get a nice photo.

I don't think cutting a cake that's on a buffet table is that odd.

I do think laying out a buffet but, not letting anyone have it until a prescribed time is odd.

So guests would know it was a fruitcake

It is usual for the birthday person to cut their own cake and again a timed buffet is not unusual. In that way, everyone has the chance to sample all the food.

Oh, come off it. OP had been standing there with the knife preparatory to cutting the cake, which is the traditional thing to do at birthday parties. You wait for her to do that and to be offered a slice, you don't swan in and grab one for yourself. There's a bit of a clue in the fact that it's a pristine cake and no-one else has come up to get a slice.

I'd be wondering if friend's behaviour is down to early dementia. What do other friends think?

Oh, come off it. OP had been standing there with the knife preparatory to cutting the cake ... There's a bit of a clue in the fact that it's a pristine cake

OP had she said made the birthday wish cut - she calls it the 'incision'. Therefore it wasn't a 'pristine' cake. And she wasn't standing there with the knife, she had gone to get some napkins.

Nevertheless, any fule kno that in that situation you don't seize the knife and go and hack a hefty slice for yourself.

I think it shows how badly you can behave and no one say anything. It’s a lesson to all us people pleasers or those with the tendency !

YANBU. It sounds like she has early stage Parkinson's (not all sufferers get the shakes), or Dementia. That would account for her changes in behaviour and appetite. My Mum has late stage Dementia and has been craving cakes yet weirdly, complains other things taste too sweet.

Eating at 8pm is not at all late, and people were told, so had the choice to eat before they came. I just cannot believe how some people complain and whine like children about these things at functions, its so rude.

The cake was not 'available', it was a proper function and that was extremely rude.

Even at home we let the birthday person cut the cake and pass it round. At a party you absolutely wait until it's been cut up and offered round or invited to help yourself. Everyone else managed to wait. It's called manners. And basic ones at that.

Exactly. Entirely different. Cake as a buffet dessert, is not a birthday cake!

They had sumg happy birthday, put out a knife and the birthday girl disappeared. I don't think thetes anu universal rule that applies here

Ah, OK, thanks for clarifying. I didn't read it that way initially.

I'd have thought most people know you don't start cutting into a birthday cake before the birthday person. It's pretty much a no-brainer really.

What do you mean by no one else knows how many people are there? Surely everyone can see this?