I could be wrong but looking at the raw, I feel like it's more of her speaking in kansai-ben than speaking formal. Maybe the translator didn't know how to show that change in another way?Ei's speech patterns are weird. I always thought that it was like that thing where she tries to be formal and proper in front of other people but when she gets flustered she reverts to her natural dialect (which makes her sound like a bit of a bumpkin or whatever). But here she flitters back and forth between them and her thoughts are even in her weird, overly-ornate "formal" speech that makes her sound like a Shakespearean character.
I just don't see the pattern with how she speaks in which manner.