[@Ponn]

Basically Suzuya is the ultimate case of her Grimoire overwriting her personality and thought process. So she's far more Tomoe Gozen then she is Suzuya when transformed, like Suzuya is taking the backseat. So when she's Burning Heart she looks at Xoyls with Olivia together in battle and thinks they are a beautiful couple who nothing can seperate. 

Also while Burning Heart is a lot more confidant then Suzuya and thus isn't flubbing her recollection of English classes with doubt, I think she's been speaking nothing but Japanese while transformed. It's why she speaks in italics and I think I mention she's talking in the language of her homeland

EDIT: Looked back and she has spoken plain english when talking to people. So yeah, she's just blustering a lot less.