Catherine Tate is a brilliant mimic and voice actress, so she's not just 'trying to imitate' a Yorkshire accent - she's got it spot on. This is not dialect, by the way, and it's not even a broad Yorkshire accent. In fact, she's speaking standard neutral English, but using a middle-class pronunciation common to many people in the north of England. It's characterised mainly by the 'u' sound in 'cup' being pronounced like 'coop', and the 'ai' sound in 'my' being lengthened and flattened to something close to an 'eah' sound. As for the phrase 'dem's da breaks', meaning more or less 'Well, that's life', the whole joke is that this is NOT from Yorkshire. It's modern US street slang, pronounced like a young African American rapper might speak - so it's as far away from something her 'old dad' would say as you can possibly get! The joke is in the unexpectedness and incongruity of the expression. It also underlines the comic irony that she is a woman who thinks she knows what is going on, but in fact she is very much missing the point. Her misunderstanding about this phrase is in line with the whole joke of the sketch i.e. her massive misunderstanding about who her new boyfriend is. We, as viewers, realise all this, but the joke is that she doesn't.

She said : "dems da breaks" (them the breaks) which means "that's the way the cookie crumbles". See http://www.urbandictionary.com/define.php?term=Them%27s%20the%20breaks You have to accept the way life turns out for you. The joke here is that it's a modern street expression which does not come from Yorkshire (or even the UK), and so her dad would never had said anything like it in his life.

She said "thems the breaks" which can be an expression to express either luck or misfortune about a situation. Hope that helps :)