3 year old very rude to a particular friend of mine

[MaeBee]

hi there,
my 3 year old usually gets on with all my friends but i have one in particular, K,who he is absolutely horrible to. she's a very close friend who comes over nearly every day, and my son is totally mean to her. he will either ignore her or just be very rude. it's particularly sad for her when she's about and other friends are about too, cos he'll single her out for this treatment. she was over the other day and so was a friend R and my son said "Daddy can play with the playdough, R can play with the playdough, Mummy can play with the playdough, but K can't." this is a typical exchange.
i don't really know what to do about it, i've mostly tried just ignoring it so that i don't reward him with attention but sometimes i do just have to tell him off for it. the only other time i've seen him do this is he can be like that to his father when his father is around.
my son is very 'into' me if that makes sense, he seems to want cuddles a lot and attention from me,and is always telling me he loves me. i'm guessing he sees my friend K as a threat (there was once a romance between us and something of that still lingers) in some way.
do i carry on ignoring it and hope he just gets over it?

Sorry, I've only just stumbled across this and I don't have children myself but do have nieces and nephews and I'm also a former Infant teacher. I'm in a similar situation, that my nephew (the same age as your son) blackballs me. It's always when he's been made the centre of attention for any reason, when the whole family are playing en masse and he's deciding the rules. It's a power thing I think and it does annoy me a lot when people laugh and his parents don't tell him off. So I would second the advice of the previous poster and make it clear to him that it's rude and not acceptable, the old "if you can't say anything nice, don't say anything" routine. Even at three, children aren't too young to understand kindness and manners. I'm sure you know that anyway, and I'm in no way trying to be disrespectful.

Maybe your DS sees something you don't?

My brother left our mum mortified when he (also aged 3) approached one of her friends one day when there were a group of them at our house and said straight to her, 'I don't like you'. But turned out he was right! She was a wrong'un!

(Probably not massively helpful I know, but I do think children sometimes are better judges of character than adults - my mum always says if kids don't like you, you've really got to worry.)

I agree with emsy. Little children can be remarkably perceptive. Especially if it is uncharacteristic behaviour.

oh she's not a bad one, but she can be a bit selfish and take me for granted! maybe he sees that!
i think maybe we started it, foolishly, by joking that she was the naughtiest person ever (after she poured tea into my plant pot) and maybe DS since then sees her as trouble. also, i think i used to prioritise her a lot and give her more attention than most of my friends (she is extremely pretty!) although my crush has toned down a lot now.
i will try being firmer with DS and tell him off when he's mean.
thanks!