Really? You think it's a good idea to be so open about feelings towards other people? You might find that there are laws against such things. There's a world of difference between telling someone to their face what you think of them, rather than airing opinions on an internet forum. If being open and honest on a forum makes me a "spineless keyboard warrior" then so be it. I'm just putting forward a counter opinion to those who seem to think the sun shines out of celebrity arses. You like her; I don't. That should be as far as it goes.
Libel laws apply everywhere.
The only difference with the internet is they are largely unenforceable.
The problem is publication, you can say almost anything you like directly to Mrs Beckham provided no one overhears it.
It used to be deemed that a sealed letter addressed to a named person could not be libellous, but the same content on a postcard could be libellous because the postman could read it.
Which is why I suggested the modern equivalent of the sealed letter - an email.
However, you are entitled to a published opinion, used to be called 'fair comment' now called 'honest opinion'.
Your remarks about Mrs Beckham probably don't cross the libel threshold, although I wouldn't risk making them, not least because libel is very much open to interpretation, which could go either way if the matter found its way to a court.