The British Isles have at least a dozen accent groups with many sub-divisions of accents - in my home county, we have at least 3, all under the "Geordie" subgrouping. London has a few that are intertwined with what we call Estuary English; the English found around the estuary of the Thames in Essex, northern Kent and east London. What she speaks sounds to me like a mix of this accent, plus the east Midlands accent - Lincolnshire mixed with London, which is fairly unusual. However, it's what we call a stereotypical "chav" accent which, to be honest, has fallen out of use in the past few years (at least where I'm from). It did used to exist, but I haven't heard an accent like that used since I was about 14.

She speaks "chav".

Cockney rhyming slang really exists and is the same for both the speaker and the listener. You can't just "make it up". One example is "Pete Tong" for "Wrong". This is very widely understood - in London and South England anyway. Nearly everybody will understand this to mean "wrong". In general all speakers will use the same rhyming slang for the same word. So for example everybody will use Loaf to mean "head". However, some words have many rhyming slang alternatives, and most people will be aware of the alternatives. An example being slang for "hand" which currently has 7 alternatives.