Over the last month, I've been texting daily with someone I met during my recent trip to Japan. We've only used casual language but today, she called me (name) 氏 whereas she has used 君 before. We spoke on the phone two days ago and she referred to that today as お喋りした, which I believe is the polite form of the verb?
Signs don't seem to be there that she's upset (ie. quick replies, sends long messages, etc.) but to my understanding, a shift from casual to keigo can mean you've done something to upset a native speaker. I know it's impossible to be sure without asking the person directly, but does this typically mean something negative from a language/cultural standpoint, or am I mistaking the context?
Thank you for any help.