Responses
I think the blue haired girl was probably going to marry Theo, but they weren't engaged. I'm guessing it was only said in conversation that they MAY, at some point marry because it was probably considered unlikely that anyone would willingly marry into the family like Perry has. So to continue the family line, they'd have married. Blue haired girl is acting like Perry took away her position when it wasn't even hers to begin with because the talks of marriage were before Theo became the duke.
That's right, keep those boobas to yourself freagin' eyebags bish