In EastEnders, 27th November 2008 episode, there is this scene where Shirley (Linda Henry) smashes a cake in Miranda's (Rachel Littlejohns) face.

I'm sure many of you have already seen this, since It's been on YT for quite some time, e.g. https://www.youtube.com/watch?v=9BscsgZwOHw

Today, however, BBC released the episode on iPlayer, so you can watch the whole thing in the best available quality: https://www.bbc.co.uk/iplayer/episode/b00fqmhm/eastenders-2008-27112008?page=1

EDIT: As caramba pointed out, the waitress was played by Laurie Hagen (not Rachel Littlejohns), and her character is hence called Camilla (not Miranda).

You can use VPN (I used Browsec on Firefox).
To watch it you also need to register on the BBC website (email, password and postal code required - they only check if the postal code exists, nothing more, so you can just pick any random valid one as per 2011 census).

The link above isn't a BBC link. I'm in Minnesota and was able to watch it just fine.

I'm in Canada and was also able to view the clip

There are 2 links above, the 1st is YT (which is unrestricted, but the video is in inferior quality and is edited), and the 2nd is BBC (which offers the entire episode in the best available quality, but is georestricted to UK).

So as some of you might have problems watching it on BBC's iPlayer, here is the scene in HD: https://www.youtube.com/watch?v=rLn2LFztC60

The actress is Laurie Hagen, a burlesque performer now based in Belgium.

Wow, you are right

I was using this
https://eastenders.fandom.com/wiki/Miranda
and this
https://www.imdb.com/name/nm1943407/otherworks?ref_=nm_pdt_wrk_sm
But apparently the EastEnders Fandom is wrong.

So, her character is called Camilla (not Miranda).

I don't think she deserved it. Shirley was behaving far worse.