Optional or not, they reflected her personality (and mind) at the time. She had been through a rough experience (The Last Revelation) and was framed for her childhood mentor’s murder, it doesn’t matter if they were rivals or not, it surely would have affected her. The player chooses to whether use that one rude dialogue or not, but Lara herself thinks about saying it or not...
So yes, it is a unique part of AoD Lara... ^.^