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I first thought it had an idea of "enhancing breasts" or "giving them a lift".
Thank you for the interesting phrasal verb.
Bust up would be a good phrasal verb for that.
I've never heard "bust up", at least, not in reference to ending a relationship. I've always heard "broke up" or "broke off".
"They broke up after she found out he was seeing someone on the side."
"He broke off his relationship with Shannon when she wiped out half his bank account."
It's less common I think than those, but it is in use. Do you us the noun bust-up for a big row?
I've never really heard that either, though I've heard "dust-up" before, but that's more of a brawl than a break up. To be honest, I can't really think of much else for a break-up fight, specifically. It may be just because I'm feeling dull-witted right now.
They had big row over it.
They had it out with each other.
They got into an argument.
They had a big episode last week and now they won't speak to each other.